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Intermittently, Photoshop will start taking EXTRAORDINARY amounts of time to open files, regardless of their size. This problem has persisted from CS2 to CS3, and from a PowerPC to an Intel Mac. The problem is intermittent, seeming to go in long cycles (a few months at a clip), but when it strikes, a 2k file -- or a 100mb one, curiously -- will take upwards of two minutes to open. Also curiously, an open file can be saved and saved again without any performance hit. But saving a new file creates the lag as well, especially loathsome if you're using "Save for Web" a lot.