Two units would not copy files without locking up. The third would not print except at "a snail's pace." Re-configuring the DIMMs to a non-interlaced configuration solved the printing problem.
Bruce queries whether this may all be related to more general problems with large DIMMs on this machine, including previously reported Ethernet problems. However, Bruce adds: "I've also seen this large DIMM/Ethernet problem occur with the 7600 and 8500."
Today's MacInTouch similarly reports networking problems related to DIMMs on Power Macs, especially 7300s.