You'd first have a 50% chance to aborb the spell, taking no damage and gaining the cost of the spell as mana. If that check fails, you'd take 50% damage (since the other 50% is resisted). The resistence part isn't a check, just a straight reduction on (almost) everything.
Isn't this a side-effect of that recent Microsoft update? If you have autoupdates enabled on that machine, try uninstalling the latest one.
Maybe I'm wrong though. I dunno.
I had this problem and I fixed it by using an older version of eax.dll. You can find the version I used with this link. I got it from here, which might help if this doesn't fix it.
Take out the console RPGs and fighting games and you could fit that list on a grain of rice.
Also, is anyone else shocked Starcraft didn't make it? I thought they went ape for that game.