that game must have been written by a dumb company to even relate itself to internet explorer. Whatever problem a game has, can only be related to itself or the amount of ram/cpu available, unless the game is very specially written. So you're 95% offbut of course it might be a virus you had located under temporary internet files. But i have never heard of a virus trying to harm an off-line game, and without beeing written to do so a virus will only harm performance in an off-line game through damaging amount of ram available 
Of course, i expect he's using firefox and not internet explorer.
www.getfirefox.com if you're actually using IE. You'll not loose anything changing to firefox, but instead you'll gain speed, stability and security.
