I recently had to completely re-install eclipse (e.g. androideclipse installed from http://www.android.com/). Before my re-install I happened to be using a user-defined add-on site ( e.g. https://broadcom-ble.googlecode.com/files/repository.xml) Everything worked as expected before the re-install.
After the re-install, when I try to reload the same add-on, the SDK Mgr appears to accept the pointer, but doesn't add it. (Progress bar starts briefly and then goes away, and when I compile, the compiler can't find the import.) Clearly there is some leftover state that I have not expunged before re-installing. I have deleted, cleaned and restarted the androideclipse install seven times now being increasingly fastidious about deleting all possible eclipse files first.
I have deleted every scrap of eclipse installation I can find including .eclipse, .android and .metadata. So I suspect there must be some other fossil file lying around.
Clearly I am missing so bit of magic. Does some guru out there know of a list of files that have to be removed to make the machine "clean". Is there some registry entry - surely not.