That happened to me.
Because of a persistent error message I got at shut down regarding the Video Engine, I removed videoengine.dll, VideoEngineDecoder.exe, VideoEngineOutputter.exe and VideoEnginePreloader.exe from “Documents and Settings/****/AppData/Roaming/Steinberg/Cubase 7_64” Needless to say I don’t I don’t use the video function in Cubase.
The error messages stopped and the drum editor problem went away 
Coincidence? Try it - just move the files to a folder on the desktop.