Two OpenGL panels on single VB form?

When I keep the objects moving repeatedly in both the two OpenGL panels on a single VB form, I got into trouble. At first, everything seems perfect, I got a smooth running report by Task manager, the CPU usuage is about 40% and the mem is 40M. But as time goes on and on, the CPU usuage goes up and after leave it run for all the night, the CPU usuage reachs 85% and the memory reachs 70M the next morning. Even though the machine won’t crash but the app slows down a lot.

What should be blamed then? Run two copies of same program by VB but a single OpenGL panel have no problem.

With almost the same operations and a single OpenGL panel by MFC, no problems either.

Where should be the problem be? The GLint OpenGL card? The Win NT4.0? The Visual Studio 6.0? My application program? Actually the program is based on a sample from MSDN.