Thread Limitation in Pocket PC 2002

Question

Currently, I am doing some research on smart Device Application, and the area I'm looking at was Multiithreading in PPC2002. I always facing problem when I create the 5th or 6th thread on my program ( while the first 4 thread was still running ). My application was just hang and not responding. Is there any limitation on PPC 2002 in managing the number of concurrent threads? Is there any recommendation or workaround to solve this problem? Or any precaution step to avoid this problem. Thank for the help.