Try specifying a different whois server to use. If you don't, the whois command uses the default whois server whois.crsnic.net, which seems like it never has the entries that I'm looking for.
I use whois.arin.net to do most of lookups like this:
whois -h whois.arin.net 123.456.789.123
Depending on the ip address you might have to use a different whois server, for example you might have to use the whois.apnic.net server to find ip addresses in asia. Unfortunately I don't think there is one end-all whois server that has every single ip in it (that would make too much sense), so you kind of have to fool aound with it. www.geektools.com
has a web interface that automates that for you and is a pretty handy tool when you need it.