Nokia 9500 bluetooth malfunction?

[mdrxp]

My 9500 bluetooth does not seems to be stable, i notice that each time when the usage (bluetooth headset) exceeded 5~6 minutes, the bluetooth connection will drop by itself, very annoying:mad:

has anyone experienced this before, by the way, my firmware is:
V 05.22(01)
03-06-2005
RA-2

Thanks.