this has happened to me a couple of times, usually when i have been browsing in landscape mode, switch apps and use portrait mode, and then quit the app and switch back to the browser while still in portrait. as soon as i rotate landscape it has always rendered just fine, and then a spin back to portrait and the page usually keeps up...not sure if it is a just a small bug in the display software or what, but it hasn't ever been a permanent issue that required rebooting or anything...
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