.htaccess redirect problem on Wordpress site

Project Description:
I am having a problem with .htaccess redirects on my site. I have a codeigniter site in the public_html directory, and a wordpress site in the /blog/ directory. I am trying to redirect all www.tastyvite.com requests to just tastyvite.com (ie stripping off the www subdomain). But it seems to be working inconsistently:

These work:

http://www.tastyvite.com redirects to http://tastyvite.com
http://www.tastyvite.com/taf/recommend.php redirects to http://tastyvite.com/taf/recommend.php
http://www.tastyvite.com/blog/ redirects to http://tastyvite.com/blog/

This doesn't work:
http://www.tastyvite.com/blog/simple-survey redirects to http://tastyvite.com

So there is something in an .htaccess rule or the wordpress setup that is messing up the wordpress redirects.

There are three .htaccess files that could affect this, one each in:
/
/public_html/
/public_html/blog/

There are also some wordpress security plugins enabled.

I need someone who can quickly fix this. For someone who has a good understanding of .htacces redirect rules, this should be a simple fix.

Please quote the word tasyvite in your bid so I know you have actually read this. Thanks!