Strangeness in register "balance" column

[Mike Sabin]

I am encountering some odd behavior in the balance column of the register
for my checking account.  A few weeks ago, I duplicated several transactions
of a recurring nature, and entered them in advance, without check numbers and
with an estimated date.  Now those transactions have come to pass, and I have
gone back and entered the actual date I paid each of the transactions, and
entered the actual check numbers for these transactions.  The balance column
is now displaying odd behavior, as if the transactions weren't sorted 
properly.  For example the balance shown at the end of a certain transaction
might be, say, $1,000.  The next transaction shown in the register is a 
check for $50, but the balance shown at the end of this transaction is, say,
$798.00.  None of the sorting options given in the Register -> SortOrder 
menu seem able to solve the problem.  By comparing the balance amounts for 
the various transactions with the transactions themselves, I can see that 
it's not that the amounts listed in the balance column are utter gibberish.
The balance amounts are correct, just for the wrong transactions.  It seems
to me that the balance calculations have somehow not been updated when I 
updated other parts of the transaction.  Am I making sense here, or am I
just being an idiot?

Bottom line: if my balance is $1000 before a $50 transaction, my balance 
should show $950 after it, assuming standard sort order.  Right?

Thanks for any help here,

Mike Sabin