battle crashing

[Giorgios]

probably been asked many times before but...

Whenever I try to play a battle on either Medieval II or Kingdoms, the game crashes and I get "Medieval II encountered an unspecified error and will now exit"!
The game worked perfectly until a few weeks ago, what has gone wrong?!

I have little experience with drivers, graphics cards etc, so an "Idiot's Guide" to solving the problem would be appreciated. My computer is a fairly new Windows Vista, so I certainly don't want to risk damaging it...

Thanks!

[Ificratis]

Only in the battle? in witch stage? in the loading of the battle or while you play the battle?