Laserjet M601 printer with "odd" paper jam issue.

Hi, all.

Here's my issue:  I have a Laserjet M601 printer that gives a 13.A2.D2 error when printing from tray #2 ONLY when 3 or more optional feeders are installed.  With 6 or 5 total trays, the printer prints fine from trays 6,5,4, and 3, and gives a paper jam error from tray #2.  With only 4 total trays installed, tray #2 prints fine.

I've tried removing optional feeders, one at a time, in order to see if one particualar tray is flaky.   It doesn't appear that any individual feeder is the culprit. 

Incidentally, it also doesn't matter if it's a print job, a config page, or an engine test.  Paper jams in tray #2 in all cases.

Any thoughts?

Thanks!