@Piper:
I tried what you suggested. If I only backup mimeTypes.rdf and delete it, the only difference is that icedove asks for each type of attachment with which program I wish to open it. But it doesn't solve the problem: after I open 2 attachments, opening the 3rd fails again with no error message.
If I backup the entire icedove profile dir and delete that, I end up with an icedove without any mailboxes and it asks me to set up new accounts entirely. I had to backup and delete the profiles.ini file as well by the way or else icedove will complain that my profile dir is not accessible.
To be more specific on the problem I face:
If I open a PDF attachment of an e-mail for the first time, it opens. If I open the exact same attachment for the second time, it opens as well. But if I try to open the very same attachment for the third time, nothing happens. The problem is not limited to PDF files. The same goes for xls, doc attachments etc. etc.
Thanks,
Dion