This usually indicates a bug in the operating system or a lack of hardware resources.
What operating system are you running? If Windows, have you manually gone to Windwos Update and ensured you have even the non-critical updates (which are not installed automatically)?
How fast is your processor, how much RAM do you have and how much free, clean, freshly defragmented space is on your C or main hard drive? (When did you last run Disc Cleanup and the Defragmenter?)
Are you editing to your C drive or to a second or external drive?
This can happen if you have installed the K-Lite Codec Pack, which installs the Haali/Matroska Splitter. The Haali/Matroska Splitter will cause explorer to crash along with any apps when you open a window that contains certain kinds of video. CoreCodec also installs the Haali/Matroska Splitter. So if you have the Haali/Matroska Splitter installed, does uninstalling it fix the problem?
You will have to search for a file named "splitter.ax" possibly in a folder: Program Files/Haali/MastroskaSplitter
I think you can use the CodecTweak Tool to disable it, but I use the following command from a command prompt in the folder where it resides: regsvr32 /u splitter.ax
My operating system is Windows XP Pro SP3.