Sometimes the Netconnection Debugger simply stops working. I will be viewing data in it one minute, run a piece of remoting code, and ... nothing! These little coffee breaks are annoying and it took me a while to figure out how to fix it. I tried rebooting, repeatedly restarting flash, replacing files and libraries and reinstalling the remoting objects - nothing worked, until....
Don't get me wrong, the Netconnection Debugger is a nice handy view of data for working with flash remoting from inside the flash IDE. I would prefer a less "prettied-up" view - a raw trace is more to my liking. Still, it does the job and gives you copious amounts of information - so I give a 4 out of 5.
The fix is to delete the "local shared objects" that are created. There is a localConnectoin object that is being utilized that ports the data from the movie you are testing into the swf housing the debugger (yes - it's just a swf file). the file has an extension of *.sol (ironic eh?) and it is found in amongst your user files.
On a windows installation it's "documents and settings/<%username%> /Application Data/Macromedia/Flash Player/#sharedObjects/.... You can delete all the files you find here - rather like deleting your cookies on your browser. You can also poke around and look for specific files that pertain to your dilemma. I suspect it's the ones under localhost since your IDE is operating under that domain. I usually delete them all to be on the safe side. Close the debugger before you do it. When you open it again it should be back from its break and ready to work.