I had this same thing happening to me, and thought it was a virus or malware, but then just as I was about to close Firefox to run a security scan I noticed an ad for the program (which is called "ilivid" btw) on one of the pages I was browsing. My guess is that somehow this ad keeps itself locked in a kind of 'selected' state, so that pressing -enter- will trigger the ad as if you had clicked it - even when the tab containing the ad was not active. When I closed the tab that had the offending ad, the problem went away.

Yeah the "ilivid ad" is exactly the same thing I get if I just push enter once I will get 3 tabs opening up, its annoying. Is there any fix for this?

You have to close the tab that contains the originating smaller ad, not just the full page ads that pop-up in new tabs. Its likely on a site that you were browsing on purpose, one of those small ads you see on almost any site - you likely didn't even notice it on that site. Its a small flash-based ad which I'm guessing is how it uses the keyboard to trigger itself instead of needing to be clicked, and somehow the ad is always 'active' even if the tab containing it is not. I suppose you could disable flash to get rid of it, but its easier just to close the page with the original smaller ad.

it was kat.ph, I had it open but now I closed it and the problem is solved! thanks

Good, I'm glad I was able to clear it up. btw, the reason I edited my answer (apparently after you already responded) was because I wasn't sure if I'd get yelled at here for specifically mentioning another site, especially given the notoriety of torrent sites, even though there are legitimate uses for such sites. LOL I was wondering if you had by chance encountered this on the same site that I was at ;)

I found a more permanent solution - You can type "about:config" (minus the quotes) in the URL box and press enter. This brings up a LARGE number of FF settings that you can modify. If you scroll all the way down to the setting named "plugins.click_to_play" you can right click the setting and select 'toggle' to change it from 'false' to 'true'. This means that whenever a page loads that contains flash or java, you have to click it in order for it to be played. This includes youtube videos. This will prevent the above ad from triggering automatically whenever you hit enter and it also prevents other video or audio ads to play automatically when the page loads.