error 404 on all pages but home

Hi,

I have started to get error 404’s all of a sudden

RewriteEngine On

RewriteBase /

RewriteRule ^index.php$ – [L]

# uploaded files

RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin

RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]

RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^ – [L]

RewriteRule ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]

RewriteRule ^[_0-9a-zA-Z-]+/(.*.php)$ $1 [L]

RewriteRule . index.php [L]

The other wp-config code is in there – not sure whats going on !? It used to be working, now it aint. Every page does it bar the home page.

What are some possible causes for this ?