Hmm, I have this problem but it's mainly when there's like seven or more rabbits on the screen on my 56k, it slows it down considerably, and even freezes it sometimes. I get this when Hosting Survivor, and when this happens I just sit out.

I have not been able to have JJ2 freeze like that after I took out a faulty copy of JJ2 from the registry and JJHH from the registry too. Could it be that in yours it starts at 1.21 and when you upgrade it adds 1.23 and it's confusing XP? I haven't had too many freeze problems ever since I took them out.