To continue the ZOC theme below it is apparent that some mariners switch off once everything is digital. When I worked in Geodesy we used to call them GAGs, GPS Assisted Groundings. There weren't due to errors in the GPS but in navigators' misundering the (then) very poor accuracy of GPS (due to Selective Availability) and the fact that the charts they were using weren't necessarily on WGS84 Datum.
And to my post title. Again, I'm not referring to groundings due to errors in the ECDIS, but errors in the misuse of information displayed on ECDIS. For example, CFL Performer ran aground on Haisborough Sand (E Coast England) in May 2008. The Marine Accident Investigation Branch report puts all fault on the fact that too much reliance was paid to the ECDIS without the mariners knowing how to use it properly nor having reference to any other navigational aid (they had their echo sounder off for example, hello?). Or the Pride of Canterbury which recently hit a wreck displayed on its ECDIS; or rather, it would have been displayed if they hadn't switched off the wrecks layer. In their 'defence' they state they were only using it as an aid to navigation but it's no excuse when you have paper charts on board.