Instructions
Download and unpack the Clear Cache batch file. When asked which directory you want to unpack the files in, navigate to "%appdata%\runic games\torchlight\mods\." Double-click on the batch file named "Clear Cache" to clear the cache. This automates the manual process.
Go to "Start -> Run," then type "%appdata%\runic games\torchlight\mods\." Make sure file extensions are showing, then sort by file extension.
Delete all .adm and *.cmp files in this folder to clear the cache.