You are talking about BT devices "seeing" other devices which they can't necessarly pair with.
iPhone BT profiles in the 3G and 3Gs with firmware 3.x include: HFP (hands free for telephone), PHAB (phone book access), A2DP (stereo music), AVRCP (remote control for stereo headset), and PAN (personal area network for tethering).
iPhones don't sopport FTP - file transfer protocol via Bluetooth. Airsharing and other apps like it connect via internet - cell data network or WiFi, not Bluetooth.
Can you connect your 3G BT with a headset? If not, do the basic troubleshooting - reset phone, reset all setting, restore from backup, restore as new.
http://support.apple.com/kb/HT3647
http://discussions.apple.com/post!reply.jspa?messageID=10701494