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To which I'd add that if you use any third party DLLs be scrupulous about checking for any lingering dependencies on the C6 runtime.
Bruce went over some of the common template issues including spurious #SEQ attributes and missing END statements, as well as some of the window and report definition errors you may encounter.
Any time you get an unknown template error on converting an app, do not save the app. Get the necessary template and try again.
A must-view for anyone with apps to upgrade. Look for the recording at http://clarionlive.com/