Issue with multiple domains

I am hosting a wordpress site at http://www.nau.tv and have an alternate domain http://www.thinknau.com, that should take you to nau.tv. On my FTP everything seems correct. The thinknau.com root folder shortcuts to the nau.tv root folder.

When visiting thinknau.com, the url remains thinknau.com (which should switch to nau.tv) and will not load any of the vimeo movies on my site. The page seemingly loads fine but the problems reveal themselves when clicking on a portfolio item. Visitors to http://www.nau.tv have no problems.

How can I just have visitors who try to visit thinknau.com be taken to nau.tv

Because I was unable to figure out what was going on, i tried writing a conditional htaccess command, but this resulted in a looping error.

Thanks in advance for you help!