When it moves into the regen step, does the software crash completely or does it just hang up? If it hangs up, what's the longest time you let it grind before deciding it wasn't going to do anything?
Try these steps, in this order: (back up all of our customizations first)
1. Reset to defaults (generally found listed in the Windows Start menu)
2. Perform a Repair (go through the motions as if you want to uninstall, you'll see the 'repair' option along the way)
3. Do a reinstall
If none of this fixes your problem, then to me that implies that there is an issue with one or maybe even both of the files.
If that ends up being the case, try this:
1. Run the AUDIT command on each file, and tell it to fix all the errors it finds. (Note, this is the Vanilla audit, not to be confused with the ACADE command 'electrical audit')
2. After running the audits, purge everything out of the drawings that you don't need, using the command PURGE.
3. Run AUDIT again, per drawing.
If none of this works, I would then open up a case with Autodesk concerning the problem.

Jim Seefeldt
Electrical Engineering Technician