My combat replays are extremely slow on WinXp

[Beorne]

I don't think it is a bug because my friends do not have this problem. My PC is not too old (2 yrs) and has 2Gb of memory, I do not have vista and I don't experience big slowings on other applications.
When I come to a combat replay with more than some hundred of units the figthing almost stops down. I experience, in fast forward, about one spell per minute.

The curious thing is that if I repeatedly press 'f' of fast forward, switcxhing it on and off, I can accelerate a little the action, about one action per pressings if I click every other second. Very strange.

Some hints?
Thanks.