All Modules crash the client (exams, sysmanager etc)

Very annoying issue, and one that seems to come back after every update. Modules outside of the SIMS front end - Exams Organiser, for instance - refuse to work and cause the main front end to crash out.

I have already checked the SIMS.ini and Connect.ini files, which are the first port of call for these issues and have resolved it in the past, so please don't point me to KB. Connect.ini is in the Windows folder and points, as usual, to the mapped drive for sims. Sims.ini is in the Windows folder and also the prog file\sims .net folder, and the links inside point to all the right places as far as I can tell.

When you try to launch Exams Organiser, you get the fault code 1573-0499-9000, for which there is no result in the Capita support site, and the description: The system cannot find the file specified : System.ComponentModel.Win32Exception.

The exams exe file is in its usual home in program files\sims .net. Capita are dragging their heels responding and we're getting a little anxious. Anyone got any ideas?

And as often happens, the solution presented itself while I was working on something else - running SIMSinst again put everything back in place, though that in itself would only run when logged on locally and didn't like the network user I was logged in as - kept saying it couldn't find simsinfrastructuresetup, even though it was there in the same folder as simsinst.

Exams O definitely prefers to be upgraded using an admin account with full rights over the C drive.
When you get the error again, can you click on more details and there might be some more pertinent info in the details about the file required and or process being used to access.