Hmm, that's odd. The profiler actually won't show the browser window until it sees that it can connect to the port that you've told it to use, so it's accepting at least one connection.
One possibility is that you're seeing an issue with IE that I've occasionally seen. Sometimes (in circumstances that are unclear to me), IE will let you close all of its windows but will continue to run in the background. This also changes its behaviour when opening new windows: they get immediately closed and then redisplayed by the version in the background. To the profiler, this looks like you've deliberately closed the session and it then stops profiling. The solution is to use task manager to kill all instances of iexplore before profiling the application.
Apart from that, I'm not sure what could cause this particular behaviour. Is there any indication in the event log as to why the instance of w3wp that the profiler started stopped working? Does picking a different port to profile on make any difference?
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