Well, I believe you have the habit of reading release notes and pay attention to what was written in SnmpSharpNet’s one.
http://www.snmpsharpnet.com/node/57
Then you should know that in almost all cases Dispose or using must be used for UdpTarget objects. However, many users ignored this tip and experienced socket problems (http://topic.csdn.net/u/20110114/15/7871705d-c71d-4e27-b01c-bf10fd108e07.html).
Luckily #SNMP (http://sharpsnmplib.codeplex.com) uses a different design which is free of such issues, so you can feel free to try it out.