rt_tulip.o hangs while receiving packets

[omill@ewu.edu]

Hello :
 For those of you who tried/looked at the rt_tulip.c written by 
Alex Bernal -- does anyone gets the workstation that is a receiver 
hanging after 1-2 seconds of receiving packets?
  Any ideas why does this happen ?
  

Another question that I have is 
   -- how to determine what critical sections are in a rt_application?
How do I know  that this operation should be done without interruptions?
I know this question is way too general, but may be, someone could give me 
hints.

Regards
Olga