Proxy/Caching Problems

We are using WordPress in a corp. environment. All was well until a new Microsoft ISA proxy and caching server came into the picture. Here is what seems to happen: You create or edit a post, and click ‘Save and Continue Editing’ when you do so, the browser does a POST to WP, and then WP sends a 302 redirect so your browser does a GET to pull the post and display it to you. The problem is, the proxy ends up caching the url, so the GET does not actually show what you submitted after the first edit. The proxy sees the same url again and just serves up a cached version instead of hitting WP and sending you what you just posted.

I consider this a problem with the proxy server, not WP, but am looking for any advice, suggestions, etc.

(Note: Removing the proxy is not something I can do, but if it is misconfigured, and I can suggest proper configuration, that would help.)