Weird problem with *USRQ creation and job submission

Here's the scenario:

Job V holds a socket connection. It is about to submit Job C, and pass the
socket connection on to it. So (following the accepted protocol), it
creates a *USRQ, using QUSCRTUQ, submits Job C, passing it the name of the
*USRQ, then waits for a job identifier to come in on the *USRQ, so it can
transfer the socket connection.

Job C, as soon as it starts, resolves a system pointer to the *USRQ whose
name it was passed, stuffs its job identifier into the *USRQ, and waits
for the socket to be passed.

The problem: for some reason, Job C intermittently fails to resolve the
system pointer to the *USRQ.

I can SEE the *USRQ come into existence in PDM, so why wouldn't Job C be
able to see it?

Anybody got any ideas of where to look?

--
JHHL