Hi Mark.
Check your snmp configuration on the device.
You will want to check configuration on 3750 for PS /Fan / Temp issue -
"snmp-server enable traps envmon fan shutdown supply temperature status"
Those map to receiving envmon traps. FYI - http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a05.shtml
envmon - Sends Cisco enterprise-specific environmental monitoring notifications when an environmental threshold is exceeded. When the envmon keyword is used, you can specify a notification-option value.
This is from the CISCO-ENVMON-MIB, and the notifications are: enterprise 1.3.6.1.4.1.9.9.13.3
1 ciscoEnvMonShutdownNotification
2 ciscoEnvMonVoltageNotification
3 ciscoEnvMonTemperatureNotification
4 ciscoEnvMonFanNotification
5 ciscoEnvMonRedundantSupplyNotification
Please let me know if this is helpful.
Regards,
-Joe