stuck M42 lens

As I was unscrewing a vivitar 135mm lens from the camera (the pentax M42 to bayonet adapter of course remained in the camera, I understand about the springy thing to get that off with my fingernails) it seemed to be a bit harder than usual to unscrew and the focus ring of the lens sort of came loose. I didn't notice at the time and then screwed on a pentax 50mm 1.4 lens. Now it's stuck on the camera/mount. It's not that I need more force to unscrew it. The auto/manual ring on the lens is stuck on Auto and the whole setup just sort of does a 1/4 inch turn each way but not like it's unscrewing. does that make sense? anyone have any experience with this sort of thing? What would prevent the m42 lens from unscrewing, like there's something stuck in there... Grateful for any help as I've actually got a shoot tonight and would like more than one lens with me.
Thanks again

Hi,
There is a certain amout of supposition here but We will have to stsrt somewhere. I rather suspect that when you took the Vivitar of something came loose. Is your 1.4 an SMC version or a Super Tak. If it is the former, check to see if it is fully on the mount. If not the reason it is set on auto is that the lock pin on the back hasn't been pushed fully home so the lens thinks it is on an SPF or ES with full aperture metering. If so then the Vivitar did leave something which has blocked the threads and caused them to lock. Without site of the camera, it would be difficult to advise fully but if you can send me a decent JPG of the problem, I may be able to offer more help.

Regards
Kim

I'll see what I can do about rigging mirrors up to mirrors but I don't know if I'll be able to send a photo. I'm not sure there's much to see anyhow, it all looks normal except the auto/manual ring is, I think, neeearly all the way at auto (but maybe stuck not quite there, I can see part of the "m" in the word manual. When I turn in one direction the whole lens+mount moves a bit but not like it's screwing tighter or unscrewing. Otherwise, I can't get the adapter off by pushing the release on the camera (because of the springy thing in the adapter, know what I mean?). I'll pm you my phone number and if possible could you call and I'll call right back so it's "my dime" for the phone call?
Anyway, thanks for any info!
dave