exec problem with 5.1

I've got an exec configuration that runs a simple ping script to a few
hosts.

I have tested the 5.3 version extend config and don't have this problem but
upgrading hundreds of machine's version of snmp is a task that won't happen
quickly and I do still have some problems that are similar.

The problem that I have is that after a few returns the agent stops
responding entirely and requires a shutdown and a restart to get responding
again.

Thanks for any help.