SonyEricsson T68i Won't Pair & Is Not Discoverable?

Hi.

I am trying to pair a SonyEricsson T68i with an HP IPAQ 2210 PDA. I
have turned Bluetooth on and made the phone discoverable, but the IPAQ
just can't see the phone. The phone will pair with the IPAQ if it
initiates the connection, but although the devices then detect each
other and presumably set up a connection, I cannot do anything -
transfer files, use the phone as a modem for the IPAQ, etc. (The phone
will access the internet correctly on its own.)

I have deleted the pairing on both devices and retried the pairing
process numerous times, but the result is always the same. I know the
IPAQ is OK, because I have successfully set up a fully functional
pairing with a SonyEricsson P900 phone. However, the P900 will not
pair with the T68i, so I assume the problem lies there. (The phone
functions perfectly apart from the pairing issue.)

I have run out of options, and am thinking of trying a master reset on
the phone. Does anyone know if this might help, or of anything else
that I might have missed?

Thanks.