There isn’t an executable called this way…
ashavast.exe could be the correct one.

You probably still have an infection, probably a rootkit on your system that is killing avast and WSC.

See http://forum.avast.com/index.php?topic=26554.0
http://forum.avast.com/index.php?topic=25941.0

http://research.pandasoftware.com/blogs/research/archive/2006/12/14/Rootkit-cleaner.aspx
http://www.f-secure.com/blacklight/try_blacklight.html

After running the above rootkit tools if nothing is found try these.
If you haven’t already got this software (freeware), download, install, update and run it, preferably in safe mode.
AVG anti-spyware or SUPERantispyware or Spyware Terminator.