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If you browse through the user library in OS X Lion, you may see a number of .plist.lockfile files in your preferences folder. Here is what these and other plist subtypes are all about.
If clicking Finder sidebar items doesn't properly show their contents, then you may need to clear some settings files.
If you find a number of similarly named files that you would like to delete from multiple folders, the Find command in the Terminal can be used to do the trick.