The mod_snmp module is a 3rd party module. I did some googling hoping to find similar reports and I had no success.
I'm guessing something specific in your configuring is causing the module to misbehavior. Now the fun part is to figure out what. 😞 Could you give me an idea of what your apache configuration looks like? Such as number of virtual hosts, if any? Any other non-default modules loaded?
Which linux distribution and version are you using?