The balance that displays when I send or receive a transaction (to the right of fees) is different than the balance that displays in the blue banner at the top (next to estimated yield). There is about a 20% difference.
An earlier version of the client had a bug that corrupted some of the meta-data associated with some of your transactions. Look through your transaction history for transactions where the amount transferred was "0" then use "wallet_scan_transaction TRX_ID true" to correct it.
I have the same issue, although this did not fix it for me.
I have many "TO UNKNOWN" transactions that remove from my balance. using "wallet_scan_transaction TRX_ID true" doesn't fix.
I presume these are market orders that were placed, canceled, but never returned?