Im using mod_proxy to do a rewrite.

So; subdomain.domain.com/Dude

Points to;

rewriterule ^(.*)$ http://www.domain.com/member.php?username=$1 [P]

However on maybe 1 out of every 5 refreshes I get;

Bad Gateway!
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /member.php.
Reason: Max-Forwards has reached zero - proxy loop?
If you think this is a server error, please contact the webmaster.

How do I fix this?