Is anyone else getting an error on 12b of the 1040 (charitable donations)? TurboTax's fix does not work and no amount entered lets me file electronically.

I manually entered all charitable contributions and TurboTax filled in the 1040 (married filing jointly) 12b line with 300. Error! I tried changing it to 0, another error! Tried 600, which we should be allowed as our donations were over this amount. Still not working. Help!!