previous versions of the "less" command were able to read files compressed with the gzip tool. In RedHat 6.1, less is no longer able to do this. Also, after viewing a file with less, my xterm window now displays the text with the video inverted. That is, instead of black text on white background, it is now white text on black background.
Prior to 6.2, the less command in Red Hat Linux could never look into gzipped files. You're probably confusing it with zless. Red Hat Linux 6.2 introduces this feature though.