Ok, found the issue....
If the trap vom the switch i.e. 10.12.0.249 is send via SNMPv1 then the source field in Netsight show "10.12.0.249(via 10.12.0.249)".
If you use SNMPv2 then the Source is "10.12.0.249" and the alarm works.
If someone could explain that it would be great.....
So just change the switch to send v2 instead of v1 and it should work.
-Ron