had the problem today that could be fixed with the gzip workaround.
then i discovered that the problem was a blank line after ?> in the wp-config.php which produces an empty line of output and screws up the gzip detection stuff, rss feeds and so on.
when i restored the tiny_mce_gzip.php to the default (with the fixe provided here) and cleaned up wp-config.php everything worked fine ??
so look out for initial empty lines in the output of your blog ;))