Hi,

        So, I checked out emacs24 from git today, and the expected hang
 happened.  `M-x debug-on-entry RET nntp-retrieve-group-data-early RET'
 dutifuly led to a backtrace. I hit c, and it returned me to another
 backtrace. This happened two more times, for a total of 4 visits to a
 backtrace buffer, which I am now attaching.

        manoj