In fact, there are three different M lens mount "flavours". This is because of the keying-in mechanism for the finder frames. The difference is indeed the length of one of the bayonet "claws" (or, segments of flange, or whatever...).
The one closest to the milled-out bayonet lock position is shortest for those lenses that use the 35/135 position (where the selection lever on the camera front is pointing a little away from the lens), a bit longer for 50 lenses (lever straight up), and longest fot the 90 frame (lever pointing slightly inward to the lens).
If one looks inside the mount on the camera body, the little nubbin that governs the selection lever and the frames is visible, and that´s what is pushed into different positions by this bayonet claw.
I happen to have the complete set of LTM-to-M adapters for the three frames, and only the 35/135 one can be mounted properly on my Novoflex adapter. Since the frame keying isn´t used, it doesn´t really matter which adapter I use for which lens (on the G1), but I can understand why some mounts have this problem and some don´t.
The "final" solution: all adapters should be designed so they accept the 90 mount without problems; then everything else should work, too.
I don´t own an OUFRO, but I bet this is at the root of the problem there, too.
