www not redirecting

If I go to my main site (proscubasites.com) via www or non-www, it redirects to non-www and loads fine either way. If I go to one of my sub-sites (newscubamarketing.com) via www, it doesn't redirect and gives an error. Suggestions?

Works:
http://www.proscubasites.com (redirects to proscubasites.com)
proscubasites.com
newscubamarketing.com

Doesn't work:
http://www.newscubamarketing.com