Application going CPU bound with 3D perspective

I have a Qt-based application that displays a number of widgets on a screen. Think a graphical medical screen - oscilloscope, frequency analyzers, etc. Most of these widgets use Qt primitives but some use OpenGL.

One of the widgets displays data in an OpenGL widget in 3D projection mode (gluPerspective() vs. glOrtho()). On most systems, this works fine. However, systems that have the Quadro FX 580 and the GeForce 8400 GS, according to the Windows Task Manager, our software continues to increase in CPU utilization. It starts out at 2 - 4% CPU utilization, but after 20 minutes or so, it is using up one complete CPU (50% on a dual-CPU system).

If I pause the application, there is nothing happening from our application, but the CPU continues at consuming a complete CPU.

If I change the display and display some widgets using OpenGL orthographic projection (2D), our application uses 0 - 3% CPU utilization. It runs like this indefinitely.

Is there a problem with these video cards and OpenGL in 3D mode?