max_stack_depth error, need suggestion

I am using Postgresql 9.0.1 in Centos 5.

Yesterday, I got the error inlog:

2011-08-16 10:57:34 EDT [3868]: [1-1] user=vcrm,db=vtigercrm504 ERROR:
stack depth limit exceeded
2011-08-16 10:57:34 EDT [3868]: [2-1] user=vcrm,db=vtigercrm504 HINT:
Increase the configuration parameter "max_stack_depth", after ensuring the
platform's stack depth limit is adequate.

I found that I need to increase max_stack_depth. But doc says that it is a
bit risky increasing it.

Could any one please suggest me what the maximum safe value I may set in my
environment?

My Server RAM is 32 GB.