Is the problem that the lens goes part of the way on, and then won't
come back off? If so, the problem is that it has a small protrusion that
sticks in the screw hole of the mount. You'll have to find some kind of
very, very thin tool to insert in there. A tiny screwdriver won't work;
it has slip between the mount faces.

I happen to live in a house with a printing press in the basement, so
there was no shortage of thin shim-like tools to poke in there. (These
tools are used during book repair to separate glued paper from its
backing without tearing it, so they're *thin.*)

In my case, the lens was a Ricoh manual focus zoom. I located the
offending nub and removed the tiny circuit board it was connected to.

It's rude to post to usenet and ask for an email reply.