Cannot connect using personal hotspot IOS4.3.1

[3Gee]

I cannot connect to my Notebook using the Personal Hotspot feature in IOS4.3.1 , using Win XP , it connected for a few seconds , then would not connect again , "acquiring network adress " seems to be the problem

Phone displays 1 Connection in blue status bar then it dissapears , used MYWI previously , IOS4.2.1, this worked perfectly

an ideas ????