Try dialing 123456789 in your E61, mine halts after warning message
Try dialing 123456789, there will be a warning message "Number not in use" but then it didn't disconnect directly.. it just halts there for about 30sec or more displaying "123456789 - disconnect" and I couldn't make any other call within this halt time.
I found this when trying to call one of my friends’ numbers that seems to be inactive now.
So… does this happen to your E61? Or any of your symbian S60v3 mobile?