Yeah, I was lucky enough to have it resolve itself.
Maybe check with MYOB if there is a desktop version available with your subscription.
Do you receipt a sales invoice or spend money first or are you doing it all from bank feeds? IE: you prepare a sales invoice, customer pays and you match the bank transaction to the sales invoice or is it sales invoice, customer pays, you receipt the payment against the sales invoice, match bank transaction to payment received? Same result different process. If the first option, you could try receipting payments received against the invoices first before processing bank feeds. IE: Sales > Record customer payment > record the payment details. I'm not sure if it will help but I'm thinking it is one step the bank matching process doesn't have to do therefore less 'processing' down time for the system maybe?
Depening on the volume of transactions, Bank feeds are an automation process to help with bank reconciliation. You could skip bank feed matching altogether and just manually enter and record transactions ready for bank reconcile. If you're not familiar with that process maybe check with MYOB support as to how that affects things for you.
Sorry I don't have a definate answer because I know how frustrating it is.