Need www. to get site to load

Hi everyone,
I have a question about navigating to my site from the url bar. Normally I can type in whatever.com into the url bar (I use Firefox on a Mac) and the browser will fill in the rest. With my site, the site doesn't load correctly unless I add the www. before the rest of the address.

http://www.teachmetapes.com gets me there fine
http://teachmetapes.com gets me this error:

Warning: main(includes/application_top.php) [function.main]: failed to open stream: No such file or directory in e:\www\teachmetapes.com\index.php on line 26

Fatal error: main() [function.require]: Failed opening required 'includes/application_top.php' (include_path='.;c:\php4\pear') in e:\www\teachmetapes.com\index.php on line **26

**Any thoughts?

When I enter http://teachmetapes.com it loads without error but resolves to the www address. check your htaccess if you have changed this and or any redirection that you may have setup. If none of this, contact your hosting company with this question.

Thanks Kobra,
It seems to have fixed itself, which is nice, but leaves me wondering...