[gaba]

Also, it was quite strange that even the iPhone could not finish the sync. So maybe my database got corrupted somehow (this would explain why the sample database worked perfectly).

Going back to previous sneaky peek versions didn't help either.

I was even accusing MobileMe for a while, but I see now that DragonDave has the same problem on a local WebDAV server.

And the other thing: there is no way to quite OmniFocus once the sync started. There is only a [Don't Quit] button under the progress bar that represents the neverending sync. Unless there will be a [Quit Anyway] button there (which could gracefully kill the synchronization) the only way to quit OmniFocus now is to force quit it. Which probably doesn't help the integrity of the database either. :(