Try manually deleting all the files in the core/cache directory and clearing your browser cache. Then log in and check.
Hey Bob,
I've realized the issue. I was trying to change the name from "button" to something else. It seemed like all i should have to do is change the name of the three files from button.php/button.tpl to whatever.php/whatever.tpl, as well as the path specified in core/model/modx/processors/element/tv/renders/mgr/properties/button.php.
When I do this renaming, it doesn't show up in the list of output types. If I leave it all as "button", it shows up just fine.
Any thoughts on what I may need to do to rename this thing?