Nokia 3100b Tri-band difficulty

I bought a second hand Nokia 3100 phone that I unlocked using the typical software that you can find off of the Unlock Nokia Tutorials. I was in England and Germany this past month and inserted a Vodafone and T-mobile sim card in that area and did not get any signal. The phone starts up not requesting any codes, but there is not signal.... Even with my U.S. T-mobile sim card, when i try to roam internationally i can get no signal whatsoever. I try to manually detect the services (i.e. vodafone, etc.) and the phone sees it but it will not hook on to the service. It says some error "No service available (something to that effect)." Do any of you have any clue as to what is going on with my phone? Only in the states do I get signal again. It was originally locked to AT&T and now i am using T-mobile... Is there another code or some other weird issue?

Are you positive that the sim cards you inserted are active?

Yes they are active and even my T-mobile sim card is programmed to roam internationally... No signal whatsoever... Manually tho i can see the various networks, (i.e. T-mobile, Vodafone, O2) but I could never connect to them... Any ideas?

In the U.S. I can switch various carriers Cingular, T-mobile, Etc...