…as an addendum to my own post I found something useful - have a look at the following link:
http://battleforums.com/history/show/25372.html

This is a description of how to remove the little bugger. Tried it and my problem is gone.
BTW, I tried in an earlier post to attach picture where you could see the result of the Avast scanner, but attaching the file/picture did not work?! The infected file in question was located at c:\windows\system32\dxdgns.dll

/Buffalo