Virus found in avast4.mdb

avast found a virus in avast4.mdb. Unable to delete or repair it. How can a file be cleaned, which is needed for cleaning files?

I really doubt any virus could infect the .mdb file. It’s probably just a false alarm (i.e. you shouldn’t try to “clean” the file anyhow).
What is the virus announced? Can you please send the file to virus@avast.com with a brief note what happened?