Thanks pBS/
in the end the vista driver didn't help. Although it loaded ok and mceirplay said "succesful", the IR blaster weren't actually working.
It was loaded ok, the security was ok but it did nothing.
What I did was install the MCE 2005 ehome remote driver in Win7 32bit (slightly modded irbus.inf / irbus.sys with security parameters for win7) and then Mceirplay worked just fine.
I wished I could use mceirplay directly with the win7 default CIR driver but it's clearly not compatible.