upgrade to fedora 9 bash fork: Resource temporarily unavailable

[mark]

I upgraded to FC9 from FC8, I never had a problem with FC8. Now I get
this error when I try to start a python app, or do anything on a
regular basis.

I have over 13GB free RAM, and only 2GB of it is used. The box is a
dual quad core Intel Xeon 5405 with 16GB RAM.



bash fork: Resource temporarily unavailable

uname -a
Linux XXX 2.6.25.3-18.fc9.x86_64 #1 SMP Tue May 13 04:54:47 EDT 2008
x86_64 x86_64 x86_64 GNU/Linux



free -m
             total       used       free     shared    buffers     cached
Mem:         16086       3189      12896          0         42        666
-/+ buffers/cache:       2481      13605
Swap:         1983          0       1983



In /var/log/messages  this is the only weird message
May 19 10:32:16 XXX kernel: possible SYN flooding on port 80. Sending cookies.


have only 425 processes running
ps aux | wc -l
425


How to identify the problem?
thanks