Problem saving cmd files

System: Windows 7 Home Premium SP1 64 bit

I was playing around with a cmd file I created. The creation of the file and initial execution worked fine. But when I edited and then tried to save the file I received the following message:

"The process cannot access the file because it is being used by another process"

I then had to use Unlocker to kill the explorer process that was running on the folder containing the cmd file. This makes for a very time consuming process of edit cmd file, run cmd file, launch unlocker to kill exploere process, edit cmd file to fix error, etc.

Why does this happen? What am I missing? How can this be prevented?