.htaccess frustrations.need some advice.

Ok, I will try and explain this as best as i possibly can. But here are the steps leading up to my problem.

~Install WordPress
~2 Options: One for wordpress install location. And another for website address.
~Change Website address by adding the WWW. So instead of my site showing up as http:// it will show up as http://www.
~Change Permalink Settings to /%postname%/

.htaccess refuses to be written to unless I do it manually with what WP tells me to put in it. I even tried permissions @ 777 and WP still would not do it. HOWEVER. I change the website address location back to just a plain old http:// instead of how I wanted it. Everything now works fine. How can I fix this? So i can still get my www and have everything still work?

All help is appreciated.