HI I must ak you a question though what operating system are you using? What avast product are you using avast free/pro/internet security? What program version are you using?

Since you have made a topic here all ready here is the link for you to go into and download some programs to scan your computer only and put the logs back on this thread and then a malware expert will be notified and check the logs for virus or malware on your computer here is the link below it gives you instructions on how to clean your computer of malware or a virus.
http://forum.avast.com/index.php?topic=53253.0

give you some advice though next time you suspect you have a virus or malware on your computer in the future go to virus and worms forum for help with this type of thing.

some programs to run
to clean malware are:
adwcleaner save the log that up and save it to your desktop and also attach to this thread.
Malwarebytes malware free save the log to your desktop and then when you have scanned and have all the logs then attach the logs to this thread.
OTL save to your desktop only do a scan nothing else.
aswBMR.exe when you scan with it let it finish before you save the log to your desktop
save All these programs to your desktop and run them one at a time and save the logs in text document
encoding save in ANSI Save all the logs from the following programs in this.

If you need more help come on back.