stack overflow problem

what could be the possible source of this? and how can i deal with it?

i am currently doing a project wherein i interface duemilanove with sim900d gsm module.

while the program is running, at one part, the duemilanove restarts UNINTENTIONALLY (for a reason that i really don't know).

and this gives me a headache! my mentor says it could possibly be a stack overflow error, and it forces the duemilanove to restart.

any help?

any help?

Without seeing any code?
Unlikely.

Too many strings?

Are you using recursion? That's a popular topic in schools that won't fit well with the Arduino...

Turning interrupts on during a badly designed ISR can also lead to stack overflow problems, but the no one can really help without seeing the program.