I have the same issue with 2 separate Vibrants, actually 3 Vibrants counting the one I took back. I have problems connecting to either the market or internet across multiple browsers while wi-fi is on. With both phones, it seems this problem is intermittent and across different brands of routers at different locations. An example is when I try to enter the market. I sometimes will get to the market home page but when I try to pull up my downloads it comes back with an error message saying connection failed. Once I turn off w-fi it works perfect in 3G, or if I leave wi-fi on, go back to the home page and then try just a minute later it connects without a problem. To make matters even worse, the problem persists while using apps that connect to the internet such as The Weather Channel. The problem is very intermittent. Sometimes I have no problems connecting, while other times it won't connect at all until I turn wi-fi off or even reboot the phone. Both phones behave the same way. I've gotten to the point now where I just leave wi-fi turned off because it's so unreliable. I know it's not the wi-fi signal strength either as it is just as likely to happen with the phone a few feet away from the router's antenna as it is when it's 50 feet away.