sysproc* lock problems

Wondering if anyone could shed some light: We are having problems with two processes concurrently executing the same stored procedure. The second process dies with locking errors, because the first process has exclusive row locks on sysprocplan and sysprocauth (I determined this by monitoring tbstat -k). Why are all of these locks necessary to simply execute a stored procedure? Here are some additional facts: 1. The stored procedure in question does call other stored procedures. 2. Update statistics is not being run during this time. 3. Online version is 5.05.UC1X3 running on NCR 35xx. A case has been opened with Informix; just hoping for some real world input here. Thank you. Johnny London