Thanks Mac29 for the suggestion. I'll double check the take down latch and call Ruger CS for some advice. (The bite was the same place as a 1911 hammer bite. )
After looking at exploded diagram and it is the bolt stop pin which is attached to the main spring housing which bit me. (Edited)
I was talking w Nitestalker and when all else fails - give it a thorough cleaning !
. (Carbon build up can cause parts to flex under recoil)
Will try simple solution first while I wait for Ruger to respond to my e-mail.
Note: I have never had this issue w MK II and I stress test that puppy on a regular basis...MK I is much older pistol.