Rodger,
That's good information. As a first step, try renaming your Preferences folder (on your local machine) and let it be re-created the next time a drawing is opened.
You can find the location of the Preferences file by look at Workspace - About Workspace.
Screen menus will be reset to their defaults, but it's a necessary test.
I also just found this Wiki article - you might find some of the information beneficial.
Please let me know if this helps performance.
Thank-you Rodger,
Larry