We've often been asked to re-create the JobEngine.sdf file when polling goes funny. You will have to stop the services to do it, but it is a relatively simple process and won't break things if you make a backup as it suggests.
Details can be found here: http://knowledgebase.solarwinds.com/kb/questions/1455/
Followed the instructions from the KB page, but no dice. Still seeing the nodes in the Last 25 Events and in the Event Summary. When clicking on one of the nodes, I'm brought to an error page stating:
Node 582 is not in the Nodes table.
I'm still trying to figure out what is telling NPM that the node is still there, even though it's not in the table anymore.