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27 February 2012, 14:23
Just had a brain wave. Decided to run Home as administrator, this didn't make any difference, then tried compatibility mode choosing XP service pack 3. Immediately Home started it suggested I back up my device before making changes. I let it do this, and now I'm in the process of updating my maps, so it looks as though either running in compatibilty mode or running in compatibility and as administrator has solved the problem. I haven't tested just using compatibilty as I'm not certain how to undo the run as administrator, which appears to be a permanent change as the UAC widow pops up each time I start Home now.
Anyway looks like issue has been solved.