Hi Nathan,
I am not sure what is causing your error specifically - this VB error report is pretty generic. Try to catch what might be leading up to it when you start new projects and send me info on what led up to it.
It may also be stuck now due to an earlier error. One reseting procedure you can try when a SPOT project gets hung up is this:
1) Go back to the geom page
2) Press Ctrl+Q (this turns on automatic calculations and enables events). Sometime these can get turned off due to prior errors.
3) Make a minor, in consequential change to your models geometry or base reflectances. I often will just change the reflectance of the mullions by 1% for example.
4) Then when you proceed forward, the project should clear old data and hopefully work again.
Regards,
Zack