Hi all, I am developing a two form application in vb.net One form holds certain data about an object size, location etc, whilst the other is a directX screen to show the model. The reason i've done it this way is so that people can move the directX screen wherever they want on the desktop. Everything has gone well so far, but there is a big problem whenever the directX screen is slightly covered by another application. Let me explain what happens. Initially you can rotate the mesh around with the mouse by clicking and dragging on the DirectX screen. Then you move a window to partially obscure the window, everything is still ok. Then you click on the screen to rotate the model and the program give the InvalidCallException problem. I've stepped through the code and it performs the mouse down event but then exits after that. Oddly though it doesn't point to any line of code. Just to the start of the application. I'm using an NVIDIA Quadro4 750 XGL graphics card with 128mb. All the latest drivers are installed. Does anyone know whats causing this or how I can avoid it? Any help much appreciated. Cheers DRB2k2

hmmmmmmm ok
It looks like it was being called due to a conflict in threads somewhere.
I have removed the threading and everything seems to work fine now.
For anyone that looks over this in the future I'm pretty sure that InvalidCallException is a general error, I've seen it twice now in completely unrelated places.

Thanks to anyone that looked into the problem for me.

Cheers
DRB2k2