WP not fetching theme files

A real disaster – WP doesn’t see fresh-added theme files.I mean it, just created a test theme with style.css+index,header,sidebar,footer templates, try to run it in theme preview – and I get a blank screen. I press ctrl+F5, clear browser cache, restart apache – all the same. I try it on Chromium instead of FF – nothing changed.

Okay then, I copy a standard twentyten, change its name in style.css, copy it into separate folder – all runs smoothy.

Obviously, WP is ignoring the template files in the folder if some secondary template files are missing. I view it more like a bug, than a feature, for I dont remember such issues in WP 2.8

So, could you please tell me, which files are needed for theme to run? Or maybe, which hooks/functions must be present in theme, for it to run?
Thank you for your time.

P.S. Yes, I have included all that “get_header(),get_footer(), etc.” stuff in index.php