Glad the problem is solved. I know the frustration about some fiddling issues :-) I still think it was a syntax error in the pfile (the slash, etc) but you might as well be right about the locking stuff.

Did you never have problems with "forgotten" locks on files at OS level?

K, from my point of view, this thread could be close.
Yes, I have, by now I hate the word LOCK :-)