WE Keeps freezing...

If I work more than 12min or so in WE it completely freezes! This is really annoying, I am making a campaign and I always have to do the things again! Please tell me why thast happening :(

There are 3 things that we need to know before we can answer that question:

1. What OS are you running?
2. What version of WC3 do you have?
3. What are your system specs?

OS:Windows XP
Warcraft III Version:1.17

Specs:
AMD Athlon 2200+
128mb Radeon 9600SE
576mb RAM Memory
40gb Hard drive