If you use the "Insert->Link to External Data" to insert a link to a https
source that uses a self-signed certificate or signed by CA not recognized by the
Open Office then it will not work after the document is saved and opened once again.

Steps to reproduce:

1. Create a new spreadsheet.
2. Use "Insert->Link to External Data" to insert an https source that is using a
self-signed cert (eg.
https://www.dresdner-privat.de/mis/pkportal/pk/kmdevisenmetalle.mis?&box1=metalle&start=1&end=99).
A window pops up informing of the unrecognized CA signature and giving options
to abort or continue (however, no way to install the cert permanently). 
3. Select desired contents (eg. HTML_tables).
4. Content is imported correctly.
5. Save spreadsheet, close it, exit OO.
6. Open spreadsheet again - link is not updated, message to that effect appears
in the spreadsheet, but there is no information that this was caused by the
issue with the cert, there is no way to accept the cert for the new OO session.
7. Manual updates also don't work. But if you choose "Edit->Links" and select
"Modify" then non-deterministically said cert-window might pop-up or not. If not
again, no information, link just doesn't work. 

Suggestion: it should be possible to permanently install the cert in the OO and
manage such certs somewhere. Also, there should be a way to confirm the cert for
a new session always.