hi priskorn
Thanks for the update. (Almost) sounds hopeful

.
Users will need at the very least, 10GB free on C drive (under user profile) to allow for model and application running, preferably 20GB, but for comfort's sake 30GB.
I must admit, it's the first time I have seen a case where (possibly) lack of harddrive space resulted in material issues, but it may explain the model not actually showing. I would expect the sort of error you did get today, as Lumion will simply not be able to load everything to system and the GPU.
The error message indicates, and I quote
So, what is an access violation, a C0000005? This is the translated #GP code the fault handler raises, which the operating system displays as an 'Access Violation', whos numerical form is c thousand 5. Its the operating system telling you that a program has malfunctioned and tried to reference no mans land. It has nothing specific to do with any particular program, or a brand of software, this is straight from the CPU and kernel of the operating system.
So it could be a range of possibles, from lack of useable memory, poor or bad RAM, or other hardware issue. I can't rule out problems or corrupted model files, especially if lack of file space meant the files at an earlier stage were not saved properly by the system. If that is the case, we can give you some steps to take.
1. Send us by email or attach to a post the following Windows Event log files:
a) Application Log,
b)System Log.
These can be found using the Control Panel --> Administrative Tools --> Event Viewer --> clicking on Windows Logs to expand list --> click on Application, then (right hand side) Save All Events As. This will create an evtx file, zip that and send.
It's critical that the graphics driver be upgraded. Can this be arranged as soon as possible by your IT support?
Even more critical is that you are using Lumion V5.0. I understand the issue of upgrading, however, it does make it difficult to analyse and eliminate potential problems. There were some issues with the materials system (given the extensive changes that V5 involved) that were for some models only, or for some of the workflows for materials editing which have since been fixed. You can read more here:
Lumion 5 release notes. Upgrading will benefit everyone as there were also lots of enhancements done.
Even if it's arranged for just one PC so you can test the student files against current versions, that would help greatly, then see where that takes us.

Will await the student files. Once received we can test, and doing so on other PC environments, will give us a good indication of things to look at. Thanks in advance.