Did you change the nameservers of your friend's domain so that it uses your own nameservers? You can check the currently configured nameservers like this:
dig ns yourfriendsdomain.com
If so, you must enter your nameservers in the NS1 and NS2 fields.
Please note that if you use nameservers that are in the same domain (like ns1.yourfriendsdomain.com and ns2.yourfriendsdomain.com for the yourfriendsdomain.com domain), you need a glue record: http://en.wikipedia.org/wiki/Domain_...d_glue_records