This is an ongoing problem Many users are posting about it now. Be certain that you
inform the avast technical team about your specific issue. The more info that they receive the better.
IMO- Do not disable your antivirus protection in the meantime.
BTW, when I click on the <More Details> button of the pop up window, I see the "virus"
identified as: hxxp://text-findservice.com/?q
and I have changed the http to hxxp as advised by others to protect the innocent!
Do you get this exact same identification of the "virus" in the pop up window that you receive?
I also do not think this has anything to do with toolbars or Google Chrome or Internet Explorer. It occurs
on my Windows XP run system but many others have posted that "it" is occurring on other O/S s.
Also I do not run any toolbar programs and I do not run any other anti-virus programs. I hope that it is just a coincidence that the commercial to encourage me to update my avast! for just $19.99 also accompanies each pop up window!
Good luck to you (and to me!)