Okay, my teacher for our cad class at uni has just posted to us a bit of a 'quick fix' for the problem. Hopefully this will help everyone for the time being until there is a proper solution...
It appears that there is a problem with the actual default "pen set combination" in the student version of ArchiCAD on the pc. Now that i have seen the issue in front of my own eyes, i will now again chase Graphisoft with a detailed explanation of the issue, and see if they can resolve the problem properly.
In the meantime, here are the steps you can follow so that you do not have to relaunch ArchiCAD everytime this problem.
When the lines turn white on you in ArchiCAD student version.
1. Go up to the "Options" menu and select "Element Attributes" and the "Pens & Colours (Model View)". This is where you can presetup combinations of pen colours and weights (like AutoCAD etc.)
2. The pen sets on you project are most likely set to the first one "Australian Black Pens 1" or something similar to that.
3. Change the pen set to something else, for example "Australian Colour". Then click ok.
What appears to be happening is that any pen that is set to a black colour tries to reset itself as a white pen. So when you change the pen table from black colours to anything else (such as grey or pink or anything colour) then the pen appears again. The pen set combination is another part that can be set up before creating a "view set" so if you do click on a view set that has been created, the pen set will revert back to the original one, and your lines will most likely turn to white.
I know this is not a proper fix, because if you change the pen set back to the original settings, they go white again. But at least this allows you to keep working without having to restart ArchiCAD every time it happens.
