Slow screen refresh when hardware acceleration is on

I have developed a .Net Windows Forms application that cannot run with hardware acceleration turned on. The user interface will not refresh in a timely manner. For example the user clicks a button that runs a process and when that process is completed the results should be reflected on a grid that is displayed however we can determine the process is finished but it takes several seconds for the grid to display this data. If we turn hardware acceleration off the issue goes away. I have clients that have applications they run on the same machine that require hardware acceleration turned on.

How can these two applications run on the same machine yet conflict over hardware acceleration?
What types of things could cause this issue?

If our code runs with hardware acceleration turned off and not when it's on:
- your code has a bug
- you have a buggy hardware driver


If our code runs with hardware acceleration turned on and not when it's off:
- your code has a bug