IE problem with Reverse Proxy

I can access my production server through my reverse proxy with
Netscape, Mozilla, or Safari, but IE 5 -6 just gives me a blank page.
IE is fine if I connect to the production server directly. My reverse
proxy setup is apache 2.0.47 running on fedora. linux. The mod_proxy
config is as simple as it gets:

<IfModule mod_proxy.c>
ProxyRequests Off
ProxyPass / http://xxx.xxx.xxx.xxx:80/
ProxyPassReverse / http://xxx.xxx.xxx.xxx:80/
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
ProxyVia Off
</IfModule>

Any ideas what rp config issues might be offending IE?