as the lads said its the pva that the paint is having problems adherring to. i would suggest using a good quality stainblock/primer witch will stick to the pva then that should allow u to coat maisonary ontop of that
i use zinsers, its great stuff, specifically states that it sticks to glossy surfaces. its a bit pricey in johnstons, about £40 a tin, but if you've got an englintine timber yard near you they sell it for 12quid