The latest version of Chrome (which automatically updates for you) is not compatable with with one of the internal JavaScript libraries (Dojo) that we are utilizing. It is a known issue that it is affecting the GeoEvent Definition and Log pages of GeoEvent Processor Manager. We are in process of creating a patch for this that will make the pages work again in the latest Chrome (will be avialable shortly).
The workaround for now is to use another browser (Firefox or IE) until you can apply the patch.
Sorry for any inconvenience this may cause,
Adam Mollenkopf
ArcGIS GeoEvent Processor for Server - Product Lead