Confirming the issue is fixed on the newest version by deleting "c:\programdata\boinc\gridcoin.dat" and restarting gridcoin
I can confirm this too (sorta).
First a minor quibble - my pathname didn't use "C:" so the file to delete may or may not be on the C drive.
More interesting - I had not been getting the 50% problem until today, and this change did indeed fix it, but on restart I got a black screen briefly, presumably when the miner started, and a Windows message that the graphics driver (AMD Catalyst 13.9) had stopped working and recovered, followed by a message that the miner had encountered an error and Windows would close it. The Restart Miner button seemed to fix things, although the Full Speed checkbox toggle did not seem to work at first (a problem that had been fixed a while back, but may have returned).
All in all, everything seems to work again.
Nice catch on the 50% problem - that couldn't have been easy to find.