Problem With Battles, Closes The Game....

Hi
I recently bought The Kingdoms expansion pack and installed it on my computer, I loaded up The Britania Campaign and started a campaigh as The Irish, I played a couple of turns and everything was fine.

Then I attacked an English City and it went to load up the battle and then the game exits & it says "Meidieval Total War Experienced an unidentified error" & it closes the game.

I've tryed the other campaigns like the americas and they work fine & I've also unistalled the Britania Campaign and then re-installed it but its still playin' up. Just wondering if anyone has a solution??? Any help will be greatly appreciated :help: