Exchange, Novarg and EDB logs

We’ve been having some problems with our EDB lately. It keeps constantly dismounting, and when we try to remount it, it gives errors. Our log files seem to keep getting corrupted and we have to erase them, repair the database, defrag it and then remount it. We have been getting a lot of “novarg’ and “mydoom” virus attempts but GFI has been deleting them alot. The attacks are ridiculous (300 +) within an hour. Does the Novarg corrupt EDB logs eventhough the virus does not get it?