I have seen this error too. It seems it happens on Linux kernel 2.4.9 and up. When I switched back to 2.4.5 I stopped having problems.
there's been a security update on ptrace in 2.4.9 when attaching to suid programs... Simon told me his wine wasn't suid, what about yours ? there may also some issues on SMP machines ? are you both lucky SMP boxes users ?
A+