WEB POPUP: - origin ?

Hello,

after upgrade vom 7.0 to EHP2 in one system,

and after implementing notes in a CRM 7.0 system (another one),

we get sometimes in both systems a unwantred WEB popup (see attached Gif: message.gif)

with message <System News- Currently no system messages exist.>.

This is absolutly not good, but we cannot find the origin.

Any suggestions.

Thanks

& best regards

Martin