I've thought about it, and thought of something that might work.
First, Delete .ico, icofile, and ico_auto_file (which I don't have on my installation)... export them first to be on the safe side, then import the attached REG file(rename it to a reg, as opposed to txt, file), which essential resets them to the defaults.
Then, you'll need to rebuild your icon cache, using the methods described previously (tweakUI).
This is actually the possible cause for seeing some icons- the ICO files you can see are already in the shelliconcache, and the broken ones aren't.
I assume you gave up associating ICO with a program that couldn't open it anyway?
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