problem with BPM　custom UI

When session time out in portal ,

refresh the browser,

login again.  But open the task in UWL, always get error :

A possible Cross-Frame Scripting attack has been prevented. Please contact your system administrator or refer to SAP Note 1651004 for more information.

It seems some check is done,

but no problem with WDJ UI.

If I logout and login again, it's OK.

But it is not convenient for the users.

Someone can help?

Thanks