I'm pretty sure about this...
If my memory suits me well, serial numbers 12.XXX and under had this issue. Im trying to find it on CH forums.
On my particular joy, I have 2 computers at home (one AMD and the other Pentium based), tried (unsuccessfully) to make it work under XP, W98 and W2k in both machines.
If I find the issue on CH forum, I will post it.
Cheers,