Framework issue.

Not reproducible, neither with "Ooo 3.0.0 RC1 Multilingual version German UI WIN
XP: [OOO300m5 (Build9350)]" nor with "2.4.1  Multilingual version German UI WIN
XP: [680m17(Build9310)]", neither with OOo dialogue nor with WIN dialogue.

"mytest.300" will be saved as "mytest.300.odt"

@giuseppepala:
Please read the FAQ and other information linked in the left frame of this
screen; AND THEN Please contribute a more specific comment. What dialogues do
you use? Do you save as OOo document or other format? Do you save in empty new
folder?

I can be more accurate now.
I've done tests with both 2.4 and 3.0Beta versions.
The problem shows (at least in my PC) only when filenames end with the 
sequence ".x", where x stands for a number in 1-9 range.
Let's look some examples:
      Il volume nell'unità C non ha etichetta.
      Numero di serie del volume: 4429-27AD

      Directory di C:\temp\OO_test

     16/09/2008  10.43    <DIR>          .
     16/09/2008  10.43    <DIR>          ..
  => 16/09/2008  10.35           411.927 DaOODuePuntoQuattro - lotto n.2
  => 16/09/2008  10.33           411.885 mytest.2
  => 16/09/2008  10.33           411.885 mytest.20
  => 16/09/2008  10.33           411.885 mytest.300.2
     16/09/2008  10.33           411.885 mytest.300.odt
  => 16/09/2008  10.29           411.880 Ordine PriceChecker - lotto n.2
  => 16/09/2008  10.31           411.885 Ordine PriceChecker - lotto n.3
  => 16/09/2008  10.31           411.885 Ordine PriceChecker - lotton.4
  => 16/09/2008  10.31           411.885 Ordine PriceChecker -lotton.4
  => 16/09/2008  10.32           411.885 Ordine PriceChecker-lotton.4
  => 16/09/2008  10.32           411.885 prova_n.4
     16/09/2008  10.27            12.446 Rainer's comments 15.09.08.odt
     16/09/2008  10.27            12.446 Rainers comments 15.09.odt
     16/09/2008  10.27            12.446 Rainers comments 15.odt
  => 16/09/2008  10.43            10.868 Rainer's comments vol.2
     16/09/2008  10.26            12.446 Rainer's comments.odt
                   16 File      4.591.424 byte
                    2 Directory  14.168.801.280 byte disponibili
The entries marked with an arrow have no filename extension becouse OO (both 
versions named before) suppressed it during "save as..." action.

I've also discovered that my 3.0Beta version, when I select from 
menu "Help/Check for updates" command, after a little while, says that there's 
no update available but this is not true. A new version is actually available 
and I'm going to install it manually.
If there's something other I can do to help, please make me know.
Kind regards
Giuseppe Pala

Ok, now i've got the solution.
All in all we cannot even call it "a bug".

Explanation: if you save a file with "File/Save as..." command, OpenOffice.org
methodically omits to write the proper extension if you type a filename that
includes, in its last characters a "." followed by a registered file extension.

Es.: if you type the filename
    "User Guide"
using "Automatic filename extension" option, you will obtain a file named
    "User Guide.odt".
But if you type a filename like
    "User Guide ver.2.386"
OpenOffice.org will omit the extension ".odt" becouse the sequence ".386" is
itself a registered extension.

Such behaviour can result in saving documents that user could not possibly open
anymore. If you want to know it, some MS applications behave exactly the same way.

I again checked with "Ooo 3.0.0 RC1 Multilingual version Italian UI WIN XP:
[OOO300m5 (Build9350)]" and can NOT confirm the reported effect.

I'm sorry for my poor english. I'll try to explain my point one last time, then 
I'll give up.
Try this
- launch OO Writer with a new text document
- type in "This is a sample document"
- choose from menu the command [File]/[Save as...]
- the option "Automatic file name extension" must be checked
- type in the name "mydocument" and press [Save] button
- choose again the command [File]/[Save as...]
- type in the name "mydocument.thiswillbecorrect" and press [Save] button
- choose for the third time the command [File]/[Save as...]
- type in the name "mydocument.386" and press [Save] button
- close OO
- open your standard document folder
- locate the last three documents saved into the folder
- if ".386" is a registered filename extension (like is in my XP system), you
  will find these three files:
  mydocument.odt
  mydocument.thiswillbecorrect.odt
  mydocument.386
  the last one has no file extension because the filename you've typed for it
  ends with a sequence that is itself a registered file extension. If you try
  to open your three documents with a doubleclick only two of them will be
  opened properly by OpenOffice: if you want to open the third you must rename
  it manually, adding to the left the ".odt" extension.

I'm not sure that this discussion could be useful, but it was nice to try.

All the best

This Issue requires more information ('needmoreinfo'), but has not been updated
within the last year. Please provide feedback as requested and re-test with the the latest version of OpenOffice - the problem(s) may already be addressed. 

You can download Apache OpenOffice 3.4.1 from http://www.openoffice.org/download

Please report back the outcome of your testing, so this Issue may be closed or
progressed as necessary - otherwise the issue may be Resolved as Invalid in the
future.

Confirmed comment 6 with
AOO410m1(Build:9750)  -  Rev. 1565724
Rev.1565724
Win 7

With WIN 4.0.1 and 4.1.0-dev I did the test due to Comment 6 and tried to save a document at 
<C:\Users\Public\Documents\AOOo\93905 - Failure in Save As... action with auto-extension\410_2> via "Users\Public\documents...". 

Before the tests I checked in WIN system settings that .386 is associated with a virtual driver.

I did the test due to Comment 6 with OO File Dialog and was NOT able to reproduce the problem.

I did the test due to Comment 6 with OS (WIN) File Dialog and WAS able to reproduce the problem.

So effect is reproducible with 
* "AOO 4.0.1 – German UI / German locale [Rev. 1524958 2013-09-20 11:40:29]"
   on German WIN7 Home Premium (64bit)", 
   “historic” 4.0 User Profile used for all predecessor versions
*  with server installation of "AOO 4.1.0-Dev – English UI / German locale
   - [AOO410m1(Build:9750) - Rev. 1562493 - 2014-01-30]" on 
   German WIN7 Home Premium (64bit)", own separate user profile.

But I wonder whether that is an AOO bug? Does AOO have influence to WIN File dialog? I will have to read some manuals and I will have to do some further tests.

The effect is not related to "ends with number", but to "Ends with registered file name extension", like ".txt"

@Edwin:
Can you contribute a result from Linux?

Additional Info:
(a) AbiWord seems to use something like a WIN File Dialog 
(b) But Softmaker FreOffice uses a very similar Dialog design and
    gives a warning if I try to save a FreeOffice Test document as 
    document.txt (file type and filename extension do not match)

(c) already reproducible with OOo 1.1.5

Confirmed for now due to comment 10, developers will have to check whether a warning will be possible.