The Web Dynpro application 'PageBuilder' has expired

Hello

We have a SAP NetWeaver Portal 7.01 and we are running Employee Self-Service in it.

We have a VPN channel setup between the clients network (where the SAP Portal and the SAP ERP HCM servers are located) and the network of a consulting company working in our project.

When ESS is tested in the client's network, everything is fine.

When ESS is tested in the consulting company's network, we get the following error message when executing a Portal page that contains a WD ABAP iView:

The Web Dynpro application 'PageBuilder' has expired

Any idea why this issue can happen in a network and not in the other?

Thanks in advance,

Jon