Don't know, you haven't given us any information to say!
When you say avast! said, please include the full error/warning message that avast gave.
- What OS are you using? is it up to date?
- What avast! version and VPS file (virus database) number, e.g. 0436-4 (see about avast!)
- What was the virus name, what was the filename, where was it found
example (C:\windows\system32\infected-filename.xxx)?
- What actions have you taken to try and resolve the problem?
You could always schedule a boot-time scan again and let it finish its work this time.
