Close TB
Find your mail directory
Move the messages.tbb and messages.tbi files from the directory corresponding with your inbox to some place save.
Start TB again
Your inbox is still empty, but now you can receive mail again without risking to damage the existing messages.
Now you could try to restore the message in the old messages.tbb file.
Create a temporary folder in TB and select that.
In the menu: Tools -> Import messages -> From The Bat! messagebase -> point to your moved .tbb file.
Now there are two possibilities, either you get your messages back or you don't.

When you don't get them back, check the size of the original messages.tbb file in your Inbox. With 360 messages its size should be somewhere between 2 MB and 100 MB, depending on the amount of attachments (and their size) you've got. An empty messages.tbb file is 4 kB.
Do you get any error message when you try to move/access the messages.tbb, maybe from your virus scanner? It might be possible that your virus scanner blocks access to the file. In that case turn it temporarily off and try the procedure again. In itself B isn't vulnerable to viruses (just don't open attachments from microsoft, the fbi or unknown ISP's), delete any suspect messages, compress the imported messages (Folder -> Compress) and switch your virus scanner back on.

When nothing helps, get back to the forum with these data and I might be able to help you further. (Not with a 4kB messages.tbb though.)

In general the best way to avoid these kind of problems is to check this option:
Account -> Properties -> Options -> Compress all folders on exit.
It won't help with virus trouble, but for the rest...