Is all performance slow or just Internet? If just Internet, are you by any chance storing your PIE temp files in BIS? That can slow browsing to a crawl.
If overall performance is slow, try a soft reset, close running programs that are not needed (using the Switcher bar or 3rd party utility like Magic Button, Spb Pocket Plus, Wisbar, etc.), and clean out Main Memory by unstalling apps and cleaning out junk files.