Make sure the rpc service is running. (You can check under the Windows services)
If it is not, best is to set it to automatic, reboot, and see if the problem is solved.
If not solved:
try the repair:
control panel > add/remove > Avast > change/remove > repair
If it still fails:
For the ODBC to XML:
open avast4.ini (any textediter will do)
look for a line "Database=ODBC"
change odbc to xml
If it still fails, we have to dig deeper.