Problem with portal eventing on some clients

Hi,

we have a problem with portal eventing, but only on some clients.

If I deploy a web dynpro application on the same portal, that call the web dynpro, portal eventing works fine. So there is no generally problem with the clients.

But if I deploy the same web dynpro application on portal and call it from another portal, portal eventings works on some client and on some clients not.

All servers are in the same domain and the problem is not user specific! All clients are Win XP and running IE6 and seems to have the same settings.

Any ideas?

Best regards

Roman