Dialer and Browser cache is also stored in the system app. If you go into settings, applications>all applications>hit menu and sort by size, you might see that your dialer and the browser app size in the high side.
I downloaded Dolphin browser so I can store cache on my SD when I had the Droid 1 so maybe that'll help you clear up space if you find that the stock browser cache is taking too much space. As for the dialer, if you clear data or cache, you might lose your text messages so I would be careful clearing that.
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