If printing a (text) document is unsuccessful, the "Modified" flag of the
document is broken afterwards.
To reproduce on Windows XP:

- open an arbitrary text document
- Ctrl-P, to open the "Print" dialog
- For the dialog shown there, go to "Settings/Printer and Faxes" in XP's start menu.
  Revoke the permission to print onto this printer for the current user.
- in OOo, press OK in the print dialog
=> OOo tries to print onto the printer which it now doesn't have print
permissions anymore
=> from now on, the "Save" icon's enabled-state doesn't change anymore. If it is
enabled, even saving the document doesn't change this. If it is disabled, even
modifying the document doesn't change this.

The above scenario is artificial, but I in fact encountered this problem
multiple times with a printer which failed from time to time. Also, I
encountered the same symptoms with spreadsheet documents, but am not sure if it
was related to printing.