If the user tries to access using AJAX, does it work?
Note: if this suggestion helps to resolve the issue or answers your question, it will be appreciated if you select the "Accept as Solution" option. We encourage you to visit our Knowledge Base https://qliksupport.force.com/QS_CoveoSearch when trying to find a solution related and not limited to: errors, feature requests, product defects. You can also visit our Qlik Help portal https://help.qlik.com/
Sheker, I think the best course of action is to likely run the shared file cleaning tool on things to see if the fixes the bad version of the file for you, as it sounds like there is a corrupt object related to that one user, which the cleaning tool should take care of. You will need to run the tool, then stop the QVS service, switch out the cleaned version for the old one, and then restart the QVS service and test things, but I think that should do the trick.
That should have everything you need, if you are running an older release, you may want to switch the Help to that version as well just to be sure you have the correct info.
To help users find verified answers, please do not forget to use the "Accept as Solution" button on any post(s) that helped you resolve your problem or question. I now work a compressed schedule, Tuesday, Wednesday and Thursday, so those will be the days I will reply to any follow-up posts.