Kristen,This is a known bug.Copy and paste your ArcPad.apx file (via Windows Explorer) into the directory where you would have created your new .apx file. Rename it to the custom name you would have called it.Open the toolbar manager and edit the copied file. You should find that you can make and save changes without getting that error.This is not an issue with the new "design mode" (that replaces the toolbar manager) which was incorporated at ArcPad 10.0.2.