[Zope] Apache 502 proxy error

Hi folks, I'm running apache with Zope and I am now getting a 502 error very often each time I try to make changes through the manage screens. I get the following exact message: ************************************* The proxy server received an invalid response from an upstream server. The proxy server could not handle the request POST /frontpage/zindex2/manage_edit. Reason: Error reading from remote server Apache/1.3.6 Server at www.51go.com Port 80 ************************************** Has anyone gotten this kind of error before? Any ideas as to where it comes from. The weird thing is that IF I am persistent and submit the form a few times, it eventually accepts the changes. Thanks for any help, Tom