Settings->Applications->Manage Applications->All and look for an abnormally large app (more than 10-15 MB). Go into it and tap Clear Data. Should solve your space issue. As far as your screen re-draws, that's usually attributed to low memory, so close out apps when you're done. Factory reset would solve it for you too of course..
Stock Froyo 3.21.605.1, modded with custom HTC clock widget, status bar icons, and rosie
unrEVOked Forever s-off
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