Pretty sure I have the same issue, downloaded the Electrum wallet from the page that the Multibit twitter page provided when saying they are shutting down. So this is a backup of the Multibit wallet. Since downloading it, all transactions were working fine up until now with a fee rate of approx 750 sat/byte (within 5 blocks). It shows the total sum on the bottom, but when trying to send another transaction, filling in the price, being far lower than the total amount (not even 1/8 of the sum), I get the message on the bottom saying "Not Enough Funds". Is there a fix to this? Tried restarting the program multiple times and lowering the fee but still no luck, the amount I can send now is far less than the total amount showed on the bottom screen.
Any help or suggestions would be greatly appreciated, thanks.