I keep reading on couponing sites that there is a virus over at Coupons.com. I've been printing my coupons through Swagbucks and haven't noticed anything, but I'm not sure where the virus is coming from. You may want to avoid printing from Coupons.com and affiliated sites until the issue is cleared.
***Update: It seems like everyone who has been affected says a screen pops up that looks like your antivirus program telling you your computer is infected, and then if you proceed to download something to "remove" the infection, you actually become infected. If something like this pops up, close the window and make sure to scan with your legitimate antivirus program.