I was curious to see if an album was available through the UK store, so I switched to the UK iTunes store. When I went back to the US store, all my iTunes matches were gone. I'm being prompted to initiate the match process again. Anyone else have this happen? I'm using this as an opportunity to clean up my tags with tuneup, so it's not a huge deal, but I'm wondering if I should avoid switching stores until iTunes match is available in the applicable country.