I have my own 2003 server that I installed DNN.

I went into portals and created a new portal, 'DomainB' for example, and gave it two aliases (www.domainb.com and domainb.com).  My original domain, 'DomainA' is set up the same way with two aliases.

DomainA functions as it should, so i went into IIS and added the host headers for domainb to the same site.

Whenever I go to www.domainb.com, it pulls up domaina's portal.

I thought that maybe it had to do with adding the headers to the original site, so I removed them and created a new site with only domainb.com and www.domainb.com and set the home directory the same as domaina.

Again, when I went to domainb.com, I was faced with domaina.com's portal.

Any ideas on where how to fix this?

Yes, I set both. 

When originally set up for one site in IIS, I had all 4 in the host headers, but thought I had done it wrong.  That's why I changed it to two different sites using the same home dir, but the 2 different host headers.

I tried that as well, no host headers, all http traffic going to one site (the DNN portal).  It had the same results.  The only way I can seem to get it to work is seperate installs of DNN.

Right now, I have two sites set up with two differen DNN installs.  I have only domaina.com and www.domaina.com in the host headers for sitea.  I also have siteb setup with no host headers at all so all traffic goes here.  I logged into the host for siteb by going to www.domainb.com and created a 2nd portal, domainc.com.  When I go to domainc.com, it forwards me to domainb.com again.