The error message “COM Surrogate has stopped working” or “DLL host is not responding” is a strange and frustrating event. COM Surrogate errors are not catastrophic, but if these errors occur often enough, they can be very annoying.
COM Surrogate is a general term for processes called dllhost.exe that separate Windows Explorer from individual DLL hosts that are prone to failures. In particular, DLLs that work with multimedia thumbnails. There are many others, but this is one of the most common.