I have had ILs and had no issue. My 642 does NOT have a lock though. My father has a 642 with lock for many years.. many rounds of standard and +P put through it.. NO issues. I don't have any first hand problems with it, nor do I actually know anyone who has.
That being said, I did remove my father's lock from his 642 two nights ago.
http://www.youtube.com/watch?v=RVPYgohVCNM
This video is of a 640 I believe, but it helped me remove the lock from his 642 in under 10 minutes.
Have there been actual locks: fact.