Yeah, same here. I did once have my home page set to the "go to" page. It changed once I went to mobile.blackberry.com and now the homepage is set to it. I am no longer able to change the homepage setting now.
I have selected my default browser to be "black berry browser" from the list of four (hotspot browser, bB broswer,media net and internet broswer)
But even though I have selected my home page to be a different page than media net. When I click on HOME on the browser menu, it takes me to Media net home page which I HATE!!