Bizarre sysmaster/IDS 10 problem

I'm encountering a weird problem with the sysmaster database, and was wondering if anyone else had encountered anything similar. I have a database server that has a LOT of databases on it, and each database has LOTS of tables. We're talking hundreds of databases, each containing hundreds of tables. The system is running IDS 10.00.FC5, on AIX 5.2. On this system, whenever I do a query against systabextents, sysextents, or sysptnext, the engine starts allocating shared memory like mad. It takes less than a minute to fill my 400,000KB virtual segment, and then continues to add additional ones until ultimately either SHMTOTAL is hit, or the server runs out of memory. Aborting the query stops the memory from growing, but does not release any of the memory that has been allocated. After I abort, I can have no user sessions connected to at all, and the engine will still show hundreds of megabytes of virtual shared memory used. An onmode -F accomplishes nothing. I have now replicated this on two different boxes, but oddly I have not been able to replicate on two others that are running the same engine and OS version. The only differences I can think of between the systems where I can replicate the issue and those where I cannot is that the systems that exhibit the problem are more recent installations, first initialized on IDS 10.00.FC5, whereas the ones where I cannot were upgraded from IDS 9.x to 10; and that the systems where the problem occurs have expanded chunk mode "always," as opposed to "enabled" on the systems where it doesn't. Has anyone else encountered this behavior (or similar behavior?) Thanks, - TJG