I'm going to stick my neck out on this one, since I'm not part of that other forum and happen to know the answer.
(1) Don't use FF or IE, if possible. Use Chrome. It's the easiest to use JS debugger. The big failing of the IE debugger is that it can't catch and then tell you about errors that happened before you turned it on, so you have to turn it on and then refresh the page, which means you may have to do many more steps to get to the point of failure again. Ugh.
(2) Don't launch your ASP.NET page from Visual Studio. Bring up Chrome and then type in the URL to the page, even if it's http://localhost/something.aspx
Then hit the F12 key to turn on the debugger. Presto. Easy. I do it all the time.
(3) And if it's not obvious: Don't use Visual Studio as your JS debugger, ever. It worked okay back in ASP.NET version 1.1 days, but the debuggers built into the browsers--even the one in IE--are so much better than VS for debugging JS that it's never worth the hassle.