Loop redirect

I have trawled through the web and the forums but so far have not found a fix that has actually worked. My website is http://www.mydomain.com, my blog is http://www.mydomain.com/blog. My website is X-Cart based. When reading the blog any of my website links become http://www.mydomain.com/blog/link rather than http://www.mydomain.com/link.
How do I fix this? My blog/.htaccess file does not contain rewrites and it made no difference whether the WP settings included the www or not.
I look forward to some help.
thanks