Type "about:config" in the location bar and scroll down to the name "browser.download.manager.scanWhenDone". The value should be set to "true". If it's not, simply double-click the line to change its value.

If you have the Download Statusbar extension installed, you need to set the path to the anti-virus program in options. Check Options in Tools / Add-ons , then select Download Statusbar, click the options button, then the virus scan tab.

Thanks dude. It solved the issue. The problem was with Download Status Bar extension. :)

Thanks, Poorerman. I didn't realize that some time after GFI bought Sunbelt's Vipre, one of the updates changed the directory for the whole program. Looks like you have another satisfied customer.