Thanks for the reply!
Sorry, I forgot to say that I have ticked the box to listen for SNMP traps in the setup. I also tried changing the port number to a high one (11162) but it didn't start listening on that port either.
I have tried rebuilding the machine from scratch and doing a completely clean installation on a clean install of Windows 7, and I see the same issue. I will try a different OS build and see if that helps.