I'm having issues as well since I updated to 10.5.2
Prior to the update, I had zero issues with my Bluetooth connection. I use a DiNovo Edge keyboard that connects straight to MBP Bluetooth connection, I'm not using the dongle. Prior to the update, it worked flawlessly. Now my BT connection is just all messed up.
About 80% of the time, upon booting into OS X, if the BT connection is not quickly used, the BT icon has the faded look with a squiggly line going across it. When clicked, it says "Bluetooth: Not Available". A restart solves the issue, but you quickly have to establishing a BT connection with any device to keep it active. I rely heavily on the Bluetooth function since I tether for internet service when I'm not home.
No other changes were made to my MacBook Pro besides the update to leopard, and it worked flawlessy prior to the update.
Any help on this is greatly appreciated.