I had the same problem with my 97 Ford Ranger. Sometimes I could not put it into gear unless I turned it off first. Been having this problem for years. I had the clutch fluid replaced, and the truck had a complete tune up about 2 years ago. Clutch problems still keep happening off and on, just far enough apart that I would forget there was a problem. Now today, the “turn the engine off” trick did not work. I can not get the clutch to push in and I can’t get it into gear no matter what, also there is dark fluid all over the place. I had the clutch problem looked at before and they always said the same thing, “we replaced the clutch fluid and it looks fine to us”. I think the clutch locking up is a symptom of a bigger problem. We’re going to have to have the poor thing towed to have it looked at, before we know for sure.