[foxboard] problem with the fifth thread

[nunoeei]

Hello,
I'm using pthread to make a program with 5 threads but when i create 
the fifth thread, it comes with a segmentation fault.
I've tested all the paramenters that i insert in the pthread_create but 
i can't figure it out...
Does anyone know about this problem?
MAX_THREAD_NUMBER(or something like this)...is 1024!
Can anyone give me a clue about where to start?
I would be very thankfull
Regards and thanks in advance!