mod_rewrite on GoDaddy linux shared hosting with ColdFusion

I’ve been pulling my hair out for two days now trying to remove file extensions from my files. For example:

mydomain/about.cfm > mydomain/about/

I’ve got this in my .htaccess file:
RewriteEngine on
RewriteBase /
RewriteRule ^([A-Za-z0-9-]+)/?$ $1.cfm

Shouldn’t that work? I get nothing but 500 errors, and the error log only says:
”JRun will not accept request. Check JRun web server configuration and JRun mappings on JRun server.”

Can anyone please help? Thanks in advance.