Hi, we made many changes in Forest to support IPR, but since this render mode is not natively supported in Max, such problems may occur.
Basically it's a continuous trial and error process. For each fail, we try to reproduce it and include a workaround.
Anyway, there are not reported issues with IPR lately. Are you using FP 5.4.1 or other version ?
If possible, please send us the minidump
when Max crashes. It may be very helpful to find the problem.