cannot set user id: Resource temporarily unavailable (not open file/open process related)

First post, sorry to be a bother but this one has been dogging me. I have a process user (java application server) that trips a resource limit every couple weeks and need help finding what limit we're hitting.

First, this is what's running:

This is the error when jobs are run or the administrator tries to log in:

I've checked the usual suspects:

Here is what the user has for limits:

I've set syslog to trap .kernel and *. and this is all I get when trying to SU:

Any ideas on where else to look or trap what limit is being tripped?