Using the @Push annotation is not working with IE 8/9

Hi,

Using the @Push annotation with IE 8/9 fails because (we assume) websocket is not supported.
The UI hangs with the red loading indicator and the screen freezes.

I tried @Push(transport = Transport.STREAMING) but it also doesn’t work.
We work with Tomcat 6 and Vaadin 7.1.10

Any suggestions to solve this problem?
Or any recommendation for an add-on?

Thank you in advance.
Regards,
Matthias