Windows forms flickering

This issue could be down to the fact you're using the main thread of the application, to complete any processing that is required when your new forms are loaded.

I have had similar issues when attempting to update the value of a progress bar in real time, as the processing that was occurring was thread blocking. The visual effect was that of a flicker or shimmer. The issue was solved when I broke down the application so that it was multi-threaded. Once the processing occurred on a separate thread the progress bar updated correctly giving visual feedback.

I'm not saying that this is the issue, but from my experience, given what you have described could be the root cause.

Laurence