mod_proxy giving access forbidden

["gb1071nx" <gb1071nx@xxxxxxxxxxxxxxxxxxxxx>]

I'm trying out some rewrite rules, and I have one that works without [P] (but does it's work as a 302, found, but over there...)  .

 

But when I add [P], I get a 403 forbidden.

 

in the non-[P] version, I can just sniff the 'location' header to find out what is being requested.   Is there a way I can figure out what the internal proxy is request is for, in order so I can know why it's being forbidden?

 

Or... seeing as how the actual rewrite pattern and substitution is identical, is there a typical 'gotcha' regarding this 'forbidden' business, that I just don't know about (seeing as how it's my first time with both mod_rewrite and mod_proxy)

 

the rule is active under a single vhost, and the substitution is to a different vhost, all hosted by a single apache instance.

 

apache 2.0.49, if that makes a difference.

 

Thanks.