can't create new transaction (master)

[Jack]

I'm just starting my big monthly update and reconciliation, and I find  
I can't create any new transaction.  I've tried in investment,  
brokerage, checking, and credit card accounts.  I'm currently on  
KMyMoney Version 5.1.80-98b2bf741.  I see no errors or other useful  
messages to console.  Could this be an unintended consequence of an  
unrelated recent change?

Jack