You might check to see that you are calling DODEFAULT() in all REFRESHes, that this is done AFTER LOCKSCREEN is set to .F. and also that you don't call REFRESH while LOCKSCREEN is .T.. Also check the value of LOCKSCREEN in all the forms including _SCREEN.
Failing all of that, do a breakpoint debugging session of your app, stopping on the LOCKSCREEN value of _SCREEN and all involved form objects, visible or not. See if one stays .T.
>I am having a lot of problems with my forms partially becomeing invisible when another window has covered some part of the form window and is then closed. It is not a consistant thing and This.Draw in the activate does not seem to help.