I believe I've managed to chase down the bug causing transactions to show up as "Mint by burn" when they actually weren't.

The code that did up the transaction list checked whether the transaction was in a PoB block, but forgot to check whether it was the coinbase transaction, with the result that all transactions in PoB blocks would show up as "Mint by burn". I'm not quite sure why the incorrect amount appeared in the list -- but try my patch and see if it fixes the GUI bug. (Or if you don't have a gui environment to test it on, I can do it if you compile an updated windows client. Haven't got a build environment of my own yet...)

(BTW, it looks like even the check for PoB block is kind of hacky -- the check for PoS blocks calls a wtx.IsCoinStake() function, but the check for PoB is implemented as a boolean flag passed in to the function by the caller... kind of ugly...)