I made a WPF/C# program and I am using the internet control for WYSIWYG HTML editing.
it is a regular Executable program.
it works on most computers however
The first step to tracking down this issue is to determine if it's really Mcirosoft.mshtml.dll or one of it's dependencies. The best way to do this is to use fuslogvw to track the assembly load failure. It will provide detailed information about which assembly is failing.
Once you deterimen which assembly is failing, please post back with the results.
EDIT
That warning message suggests that the operation eventually succeeded. It doesn't appear to have the error in it.