Cisco SG-300 series switches resetting randomly

I posed another question recently about how to port SonicWALL to SonicPoint with VLAN tagging over a fiber connected uplink switch.  While working on this project I've somehow triggered all my Cisco SG300 series switches randomly resetting themselves for no apparent reason.

We have:
SonicWALL TZ210W
X0 Interface - LAN/DATA Network
X6 Interface - VOICE Network (Shoretel phone system on a separate network)
Cisco SG300-52 with a fiber uplink to a Cisco SG300-28 (DATA)
Cisco SG300-48 PoE with a fiber uplink to a Cisco SG200-28 PoE (VOICE)

The only connection between the VOICE and DATA networks is through the SonicWALL.

Yesterday I installed FindIT to two systems - one on the VOICE network and one on the DATA network.  I used the software to find the uplinked switches on the far end of the fiber connection.  Bonjour apparently doesn't broadcast beyond it's own subnet.

Since then ALL of the switches have started resetting themselves.  They can be up for hours or minutes.  They never all reset at the same time but they all do reset.  The logs show a "cold start" each time and I can find no cause.