Many of us have complained about this to FileMaker Inc. At the very least, we need to be able to turn this feature off. If you wish to add your voice to those who have already requested this change go to: http://www.filemaker.com/company/feature_request.html
In the mean time, ULearnIT has devised a work around:
Perform a script that includes a Pause/resume script. The script doesn't have to do anything but pause. While the script is paused, you can edit the records without the auto-sort making your records jump around. When you finish editing, resume or halt this script.