Hi,
don't worry, I'm sure we'll find a solution.
I see two important things in your post. First, you're using regular Outlook XP (not Outlook Express). This is a very important point as Outlook should be covered by the avast Outlook plugin (instead of the Internet Mail provider).
So my question is: do you see the Outlook plugin splash screen when starting Outlook? If not, can you try to go to the Outlook About box, click Disabled Items and make sure the avast plugin is not listed there? If it is, just remove it and you should be all set.
Next, even if the log file has ~200MB, I'd be interested in it. Could you please post at least a couple of hundreds of lines from the beginning of the file? I'm sure the file will have a very repetitive pattern in it so it should be quite easy to find out what was going on. My guess is that this file would also be extremely well compressible, so trying to ZIP it may actually reveal a file of reasonable size (e.g. 1 megabyte).
Thanks
Vlk