mod rewrite not working in LiteSpeed

[Ness3k]

The rewrite in the .htaccess file worked on the old Apache server, but is not working in the LiteSpeed server 4.0.20. I heard it was fully compatible with Apache. Below is the code...

 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteCond %{REQUEST_FILENAME} !-l
 RewriteRule ^category/(.*) /$1?tab=category [P,L]

This code causes a 500 Internal Server Error. The error in the log goes like this...
[ERROR] [REWRITE] Absolute URL with leading 'http://' is required for proxy, URL: /aromatherapy.html

Thoughts as to why this would work in Apache and not in LiteSpeed?

Thanks.