Shifting Problems ... Master Cylinder?

So, I went to the track Sunday and after getting back to the pits from my second pass I pulled in and then went to back up and I couldn't get into reverse. 1st was also very difficult but possible. All forward gears are accessable but difficult. Reverse can only be entered with the engine off.

The tranny was rebuilt (new synros and upgraded steel 3-4 fork), new OEM master cylinder, a SPEC Stage III w/ ceramic disk and aluminum FW all about 10,000 miles ago when I did the new motor. It all has been working extremely well with no problems. The pass preceding my problem seemed to be fine in retrospect.

After doing a search and reading posts I called SPEC and spoke to a tech who was very helpful. He thinks the master cylinder is the primary suspect. He thinks the diaphram could be bad and I am unable to fully engage the clutch.

I just haven't read that many instances of Master Cylinder catastrophic failure. And this one is relatively new with no symptoms until it failed (supposedly).

Any ideas, comments, similar problems?

TIA guys

you might want to look at the slave as well, and also I had a similiar problem that when sovled ended up being a spring from the inner diaphragm(sp?) of the clutch broke off, but you said that you could get into gear and in my case I couldn't shift into gear at all. Hope this helps
PS. My clutch was the spec III also