It seems AppVStreamingUX.exe is causing a CLR exception. There could be numerous issues causing this (missing core components/runtimes, corrupt packages/cache), but what is your main concern? Does this actually result in a GUI popup, or just an eventlog
entry? I suppose this takes place after login and when the sync-appvpublishing scheduled task kicks in. You can disable the task, but you wont get any new/updates app-v packages from your backend (which you're already not getting because of this issue).
It's strange your IT (support) department doesn't want to look into this issue, but I don't know their service level agreements ;).
Are currently published app-v packages working at all? Do you see any issues in the app-v eventlogs? I would first try to clear and clean-up all app-packages from delta-cache and packageroot. Also cleanup all leftovers in the registry. After that, perform the
following powershell cmd: sync-appvpublishingserver 1.
If this fails, have a look at the last package, which is possibly causing this issue.
Roy Essers