So, I went into Mod Tool today and went to try to open an .exp file. It gets halfway, then comes up with the following dialogue:
The code at the bottom in the red bar comes up with:
I saved a new, blank .exp file just to be sure and it will not open the new file.

I could open .exp files yesterday with no issues and I have not made any changes to my laptop since, save installing a new version of java. I tried the 'runonce' batch file but it fixed nothing. I can still import and use ZE Tools.

EDIT: I had a random thought to try it in administrator mode. It seems to run in administrator mode fine, but not in standard mode. At the moment, it'll have to be run in administrator mode.

Same problem here. I don't no why it can only open and save at the first day after installing.
But it can be a problem of Windows, too. If your Project path: C:\Softimage\Mod Tool 7.5\Addons\ModTool_Database\Scenes\UnitBase.exp is write protected it can make problems. I have the problem, since i installed it to C:\Program Files (x86)\Softimage\...
So i made a new Project path at D:\Star Wars\XSI Project\