I have a drawing in which the Zoom Window command is not functioning correctly.  When I am zoomed out, I can use Zoom W but the window is very jerky and can not be set to any size I want ... it seems to have set increments on each axis.  When I am in close, the zoom window becomes invisible, but the command is executed ( again I can not set the window size accurately).I have saved and closed the drawing, closed the programme and it still persists.Other drawings behave correctly.Any ideas on how to get back to a correctly functioning file would be appreciated.Christopher

Graphics card problem?I assume you rebooted your machine?

Yes, I did a reboot.I have selected all the entities and copied into a new file and all works as it should.  Very strange how these gremlins get into places.C

Purge / Audit didn't cure it?

I did not know about audit.  I have tried that now and it has not fixed the problem.I also tried the purge but did not fix.C

If the problem only happened in one drawing then it could not have been related to the graphics card.If you took everything from the original drawing that you needed and inserted it into a new drawing and it worked why does it still matter?  Your solution fixed whatever the problem was.  Move on.  If it should happen again I'd say it was operator induced error (i.e. - you did something wrong; you just don't know what it was).  The only way to troubleshoot that type of problem is to keep a running log of all the commands that you used during the drawing session.
John Connor2015-04-16 18:55:10

I have moved on.I want to know why it happened so as to avoid it again.Before I thought of copying it to another drawing, it was a problem.....but as you say the problem is solved.C

Like I said, it was probably operator error and had nothing to do with the program itself.  Maybe you were rushing and invoked a command without knowing it.  Maybe you bombed out of a command which caused the program to respond in an unusual way, or maybe you tried to do something without exactly knowing how to do it and you messed up your own drawing. 

I had a same probleme likes you,but my friend helped me solved it,but I don't konw how he did it exactly..