Try this, it seems to work for many, and for gods sake use search and moan in another thread next time? theres only 2525997179 threads about pretty much the same thing already
1. Uinstall the game normally
2. Delete anything EU related of folders and files (not including screenshots ofc those are safe and videos etc)
3. Get CCleaner if you don't have it and run that.
4. install EU again (I had to install in an different directory for it to work, IE it was in C: and it had to be in D: for it to work again, most likley will work as always on C: though, some have issuses and you have to change install directory for some odd reason i dont know)
5. let it patch and it should now work.
and as akoz says, get some PROPER av and run that, might be something there to, free av's are bullshit all the way, norton is worse, most of the other works swell.