A false assumption? There is no drive C!

[Ubik]

Backslash in the end helped! Well, at least the mail protection works correctly now - I assume that the problem with mail protection is the same could-not-create-temporary-file. Now i am only wondering why the backslash was missing in the first place...

Well, thank you for helping me!

[igor]

Oh, that's not exactly what I meant... I was rather trying to say that it shouldn't be there.
So, you are saying that with a backslash at the end it works, and without it it doesn't work?

What is the exact content of the TMP and TEMP variables? I mean - the content you see when you select the variables in the "System Properties" and click on Edit, not the expanded ones (both system and user, if possible).
Thanks!\

[Ubik]

I was hasty. The mail scanner actually works now without the backslashes in the end too! I do not think that I can  say anything about the updating anymore - I would not be surprised if it somehow worked now. I will try rebooting, just in case the path gets stored once it is read in. (I mean, that if Avast/a module reads it in only once, and then uses it even if the actual path was changed - maybe I should try something wild as the path to see if it is read only once.)

Here are the temp variables copy-pasted from the Edit window:

TEMP (user): %USERPROFILE%\Local Settings\Temp
TMP (user): %USERPROFILE%\Local Settings\Temp

TEMP (system): %SystemRoot%\TEMP
TMP (system): %SystemRoot%\TEMP

[Ubik]

The mail scanner still works, after changing the paths to nonbackslashed version and rebooting.