I have Xdebug 2.1 installed, and running with PHP 5.2.13. It can successfully connect to multiple DBGP clients (i.e. the xdebug.remote_log shows communication
I know that this has been answered but I came across the same issue just want to offer my answer if anyone else runs across this. I accidentally missed a case value in my paths which still allowed me to connect and run the debugger but it wouldn't stop at my breakpoints. I didn't realized it till much frustration so I just want people to know that that could be a possibility as well.