According to the author of the PanelManager, the problem is that you nested your classes.

Quote from email:
There is a fair amount of reworking to do in the code to correct the issue.

Nested Classes is what's causing the problems. It might look tidier, but VS does not like them.

There will be some Friend modifiers needed in order to keep the majority of the code working, but once there are no more nested classes the WithEvents will work just as expected.
Can you try that? That is indeed a difference between our versions so it could well be the problem (although I would find it a little strange..).