same problem here.
got a brand new dell streak UK version ( not branded ) with android 1.6. insert my simcard ( Fyve - Vodafone ) and it works with no problems. data connections, in and outgoing calls works great. now got the official froyo 2.2 update from dellsite and i have exactly the same problem like you. i used other simcards from my friends ( telekom, base, o2, old vodafone card, blue mobile, etc.) and all cards works with no problems
btw, my fyve card is the newest version, got it in january. tried my fyve card in other phones like desire hd, lg optimus one, htc trophy, iphone etc. works great
is it a baseband problem? have anyone a old basebandversion from official 1.6 version? need help plz
greetings from germany