stuff=`cat $file | grep -n "$info" | cut -d: -f1`
cat $file | sed -e ''$stuff'd'
Please don't be a process hog (and your quoting leaves a bit to be desired ;-) ):
stuff=`grep -n "$info" $file | cut -d: -f1`
sed -e "/$stuff/d" $file
Simon, if you use double quotes around the $1, you'll find sed will work perfectly.
Learn how to use quotes properly and you'll find scripting becomes much easier.