JH4music,
There IS a firmware update for your computer:
Apple - Support - Downloads - iMac EFI Firmware Update 1.1
I don't know why anyone would tell you you can't install it, it isn't hard. Hope it is what you're looking for to get your unit to work.
Not all white iMacs have the Ti chipset. There were some at the end of that production that have the hated Agere chip. Count yourself lucky if you have Ti chips.
On the other hand, I've read somewhere that Agere sort of fixed their chips in their latest incarnation, and that they'll be showing up soon in the aluminum iMacs, if they aren't already there. I'm waiting for someone to confirm that the latest al iMacs do have the new chips, and that they work ok. I've been watching this website...and at the RME forum...