-Update-
I deleted quite a few SID files and reinstalled Rockbox with the Utility. It seems to be working fine now.
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I just updated my version of Rockbox from Ver 3.0 Revision 19132 (11-18-2008) to Ver 3.1 Revision 19603 (12-28-2008). Now, when Rockbox scans the disk upon power up, it either doesn't retain the filelist or decides not to use it. When I check "View dircache info" in Debug, it says that the cache isn't initialized.