The problem is that by default webmin is set to only listen to localhost as others have mentioned. The OP should login to https://localhost:10000/ for the first time and then configure webmin to open up access as much as he wishes.
Yes, and you can even do this remotely using putty and lynx. - John -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.8.6 - Release Date: 2/7/2005