Alot of bugs using multi currency.

Hi again,
I found alot of bugs in this software using multi currency, from purchase, to mark purchase paid, to edit invoice that has been saved in other currency.

Bugs like it changes the currency of a edit invoice when click edit invoice, to the default currency, cannot mark a invoice payed as it claims the default currency value dont match the invoice currency value, i also marked one as payed that keep having 0.01 left on the invoice i cannot pay so it is marked at partially payed, and so on and so on... it has sooo many bugs when it comes to this.