Cliff from the Trimble Help Desk got back to me today and said the problem is the ExtensionPref.apx file is READ ONLY. To fix this problem with Windows Explorer you can copy that file from your GPS unit to your computer, right click on the file and uncheck the READ ONLY button, then copy the file back to your GPS unit. Or delete the *.apx on your PDA. Next time you start ArcPad a new (editable) one will be created. This is a full reset. In this case you must uncheck unwanted extensions in "advanced options" again. Günther
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