Hi there TimT, i have exactly the same problem, it is a machine specific problem, as i can get EMS on two XP machines at work, but not on my machine at home (Not annoying at all!). From other forums, it seems this problem hits about 1 in 20 machines, and, as yet, no one has found a solution.
I'm gonna try out DOSbox when i get home tonight, and i'll report back with the findings, but i'm pretty sure there is an EMM/EMS memory problem on certain XP configurations.
Also, when i finally get my internet connection back at home on friday, i'm going to do every update i can (including service pack 1) and hope that fixes it properly!