I did some searching on this error message and could not find much information. The software version on the switch appears to be a very old version. The more recent firmware includes many improvements to SNMP and some fixes where specific SNMP events would cause a switch to crash. Scheduling a time to update the firmware is the first step I suggest. [URL] Once updated, then monitor to see if this issue reoccurs.
I have a stacked switch with 6 5548P units and I monitor their status and basic info via SNMP using Spiceworks and PRTG.  Yesterday we had a weird outage where all ports on unit 4 went down (HDMI and StackID indicator remained up) affecting traffic and POE devices attached to this unit. After rebooting unit 4, things went back to normal. Then, checking the system logs, I found the following message. Has anyone seen this error before?  %STCK SYSL-A-UNITMSG: UNIT ID 1,Msg:%SNMP-F-BADTDOMAIN: Invalid or unsupported TDomain was given - function SNMPNotifyG_TDomainAndTAddress2UdpAddress 2 ***** FATAL ERROR *****  Reporting Task: CNLD. Software Version: 4.0.1.11 (date  16-Oct-2011 time  18:10:50) 0x19f5c4 0x19c228 0x6aa9f4 0x49ba70 0x4a0f3c 0x4a10f8 0x484ba4 0x5dc3d4 0x5c6d44 0x5c6fc4 0x5c7028 0x5c7204 0x5c7258 0x5c79a4 0x5c7a70 0x5c7c20 0x5bfd78 0x5bff68 0x6856ac 0x68713c 0x4ca6dc 0x4caa9c 0x1548d0 ***** END OF FATAL ERROR *****  Thanks,
PowerConnect 5548P Fatal Error - SNMP-F-BADTDOMAIN