Widgets stopped working

Hi guys,
after using RTC 3 for several weeks, the widgets on all dashboards stopped working suddenly.
The widget shows correct title, however the following info in the body:
"An error occured while loading the widget.

TypeError: _9 is undefined
File: <server_URL>:9443/ccm/web/_js/A:?etag=Q2rit_en_US
Line: 1659"

Finally the log shows the following:
http-9443-Processor17] WARN dashboard.service.internal.registry.ViewletCatalog - Could not find a viewlet definition a the <viewlet>: com.ibm.team.dashboard.viewlets.web.feed

Any ideas what happened are really appreciated

Many thank