htaccess causes loss of stylesheet

[eluser]Michael;[/eluser]
For some reason when I try to use the CI Guide version of an .htaccess to remove 'index.php' from my urls I lose all reference to my style sheet in my views:

from my template:
<link href="<?=base_url()?>files/css/default.css" rel="stylesheet" type="text/css" />

I do not have 'index.php' in the base url config, as I missing something here?

Thanks!