The first bit (up to [06:33:02]) indicates some sort of file system error, not a communication error. Basically it could not write the results to the disk, presumably because it thought the file was corrupt. Rather than send bad results back to the source it deleted them.
The next part (up to [06:33:27]) is an attempt to get another WU. First of all it has to connect to an assignment server. This then routes the request to a Work Unit server, but as the error messages suggest it could not even connect to the assignment server.
Both of these events occuring together suggest you have some inherent instability in your system, which is causing the crash. I'm guessing that you are using FAT32 file system. When your system crashes with FAT32, the last part of the file will be lost (just like with Kazaa). So F@H thinks your results are corrupt and discards them (again, like Kazaa downloads).
Suggestions:
Convert to NTFS if you are using FAT32. It won't cure the crash but it may stop you from losing your work.
Sort out your system instability - I've found from experience that raising Vcore slightly (0.025V is usually enough) can cure this problem, even though the system is theoretically running at the correct settings. Watch your temps though.
