Curious my iP4 and iP3G both running 4.01 pair happily so it isn't a problem with a f/l Z4 (07) and iOS4
Could an 05 ULF be the problem with iOS4 , interesting question
This does ring a faint bell that someone had to upgrade the ULF but can't remember why they needed to do it
Did you unpair all and any previous phones ? first before attempting to install iP4
and possibly remove any pairing on iP4 as well
I must admit the Z4 can be tricky compared to say my 120d and I have seen reports of users having to make several attempts
to get it working :?
Might be worth checking whether there is a coding update for ULF with Dealer .
Mine did have a recode when they fitted the iPod connection kit but that was the point they obtained the pair code so I can't say it worked
prior to that .