To replicate, at least on OS X:
1. Create some files in LibreOffice and save to a network volume.
2. Quit LibreOffice.
3. Make the network volume unreachable (in my case, turn off the NAS).
4. Restart LibreOffice.
5. As it tries to produce thumbnails of the recent documents, it tries to connect to the network volume. Or rather, it asks OS X to do so, which means a wait of a minute or so followed by an error message. It does this in turn for each file it needs a thumbnail of.
*** This bug has been marked as a duplicate of bug 87013 ***