When working with one of my clients that had “corrupted” his customer setting, we came across a solution that allowed him to avoid having to reset (delete) the “zup” file and lose all of his prior setup user preferences, which he had been developing over the past few months. 

What happened was that he had put a filter on a form that made it impossible to reopen the form. Since the “zup” file gets updated when you close your NAVISION client, the solution was to keep the current (corrupted) NAV client open and then open a new NAV client, that opens with the prior user settings (since the zup file had not been updated yet).

The next step is to close the “corrupted” client (which will update your zup file), and right after that you close the second NAV client (the good one). 

When you do that it will ask you “if you want to SAVE the zup file”. You should answer “YES” to that question, because then you will update the “zup” file with the good setting and override the bad setting previously saved when you closed the first client.

Hope this serves useful if you get into the same type of problem.