I'm not having quite the same problem as everyone else. My sensation can pick up and connect to my router no problem, but when I try to go to android market or onto internet, it can't connect and I get a "network failure" message. I contacted HTC, they suggested it was my router that was not allowing any more connections to it. I checked my router and it doesn't have a limit on connections. HTC told me to try a different router somewhere else. I won't be able to test that theory till tomorrow, but thought that was a rubbish suggestion.
Does anyone have any suggestions? Sensation is on T Mobile. I have a Desire on O2 which has no such problem.