I tried the try/catch thing and some other stuff but to no avail. The plugin generates the error message even before it reaches the actual Invoke1 call, so I get no exception readout in the log. While looking for angles to debug I also noticed that the plugin generates the same errors if I change the guid in VA_Id(). The plugin initializes but as soon as Invoke1 is called there's a crash, even without any profile switching. When I put back the original guid value the problem is gone again. Which seems funny since I thought the value didn't matter as long as it is unique and in the right format (I use Registry format with VS generator tool). Investigations, somewhat frustratingly, continue.
To check: The main functions VA_Id() etc. I put in public static class 'Plugin'. There are however callouts to other (static) classes in the same namespace. I'm assuming that should not be any concern, but just to confirm. Thanks a lot.