Okay, I figured out what the problem was. And it wasn't exactly straight forward.
On my form, I added the desktop grid control when I was using v126.96.36.199. When I upgraded the app to use v188.8.131.52 today, I just changed the .dll. The first time the control actually ran, and the Protected property was set to true, the next time the control ran, I ran into the problem.
The solution was to deleted the grid control from the designer, save the form, then add the grid control back into the form, changing the name of the control to what it was before. Then the control behaves as expected.
Edit: Okay, after loading the form several times, it has gone back to losing the names of the worksheets again. The fix must be something other than replacing the control on the form. I'll continue to work on figuring out what's going on. Any information that you can supply will be greatly appreciated.