When an internal error occurs, Nuendo doesn't crash immediadely but gives you the chance to save your work and restart the program. A logfile is created which lets the programmers see where the error happened in the code. It's located in the Nuendo Folder (usually C:\Programme\Steinberg\Nuendo) and is called "Nuendo.Log". So if you see this Error Warning please copy the Nuendo.Log file and send it to nuendo@steinberg.de via email. The developers will fix the problem for the next release.