We have a client who has two FMS Servers, both with CWP(XML/PHP) enabled (This is NOT a two machine deployment, but two fully functional servers on the same subnet ). They have a file on each of the servers. One file on FMS A references a file on FMS B and this works fine in FMP, but not through CWP. They can query both files on FMS A and FMS B separately via FM's XML URL, and see all fields local to that file using the same credentials. But if you place a field from the file on FMS B onto a layout in the file on FMS A, you can see it in FMP, but not in CWP. We have checked all security and everything seems in order (the fact you can separately query these files using the exact same creds helps support this notion)
We have done dozens of CWP setups, but nothing quite like this...perhaps this is a limitation in CWP, or we are missing something?