try taking the macro apart and playing with it. I have a macro named test that i use to check a macro and play with it till it does what it's supposed to

start of with no modifier getting it to do what you want

/cast [target=pbuy] renew

if pbuy gets the renew even if your targeting someone else that part works move on to part 2

/cast [modifier:alt] renew

this should only work when you hold alt and press the key it's bound to.

once you get these working try the ctrl mod
/cast [modifier:ctrl] renew

then put them together

/cast [target=pbuy,modifier:alt] renew


other than that i can't help much from work but i'll post my priests key map when i get home in an hour or 2