"Hang UP" Bug on Unloacked Treo 600

Hi There:

I am a new owner of an Unlocked Orange Hangspring Treo 600. I got myTreo 600 through ebay. And it was unloacked as it arrives. Everything is great Only to find out now that , "When placing call , once the call is in progress of ringing, I am not able to hang up the call, And when I do hang up the call, the system freezes, then require soft reset to reboot the phone again.".. Does anyone experience the same problem ? Woudl some have any idea and solution to fix this problem.. Step by Step explianation please...

Here is my Treo 600 info:

Firmware: 03.05
Software: Treo600-1.0-OUK
Hardware: B

email : jackresume@hotmail.com

Please help.. I have suffer enough from this "Hang Up Bug "