Mytop has started to break recently when upgrading from RHEL or CentOS 5.x to 5.3. It appears that some of the perl modules have change.d

There error is:
#mytop
Error in option spec: "long|!"

The fix for this is to edit the mytop script and comment out the line containing long|!

pico /usr/bin/mytop

Run a search for long|! and comment out the following line:

"long|!" => \$config{long_nums},

Start mytop and you should be fine!