to answer your question, Kevbo, i would say 'no', i haven't noticed a scripture that says we shouldn't pray 'to' the Spirit!
but i (we) have noticed 'who' we should pray to thru by the example of Jesus, Himself!
(Math. 6:9-13)
okay, now from a BIG PICTURE perspective/view:
your question seems more like a paradox than anything!
do you recall, Kevbo, in the OT when God promised that He will pour out His Spirit upon all flesh?
well, many believe that that promised was accomplished or fulfilled on the day of Pentacoste!
and even being fulfilled today!
do you recall when Jesus said when the Comforter comes, He will bear witness to me (Jesus)? He will only speak of things concerning me! He will bring back to your remembrance things that i've shared with you!
well, doesn't that makes since? that the Spirit will speak of the things of Jesus? since they are, after all, one?
to me, it is a very fine line to separate them!
the Father from the Son from the Spirit!
tho they have specific roles to play and tho they are in specific order, they are one!
and since they are one, praying to the Father is praying to the Spirit! or praying to the Father is praying to Jesus!
but look at this:
Jesus, in the flesh, told us and showed us how to come before our Heavenly Father!
He said say Father and use my name (Jesus)!
and unbeknown to us or whether we know it or not, the Spirit of God leads us, urges us, helps us to pray - whenever we pray!
thus, the glory is all God's!
because, truthfully, we have no power to do anything!
Paul said that it is no longer him (us) that do - but it is now Christ wihtin us that do!
that is, it is the Spirit of God within us that do!
we simply reap the benefit of the 'joy'! rejoicing!
while God do the work!
we give Him our little faith and He takes over!
the disciples believed Jesus, that is why they were able to do miraculous things!
but it wasn't them, it was Christ in them!
Christ, Himself, said that i will be with you always, even 'til the end of the world!
so, when we talk about praying to the Father we must include the Son and the Spirit!
for where ever one is, the other is also!
Jesus just showed us how to get personal and intimate with God! He showed us the way! not a fleshly way but a spiritual way! and He (Jesus) showed us while He was yet in the flesh!
okay, i hope i didn't complicate things!
i hope yousee what i'm saying!
what do you think?
