I have Keystroke POS running in a SBS2003 environment and we continue to have problems with files locking or network connections timing out. I have contacted the company and have worked through the resolutions suggested. They don't have a lot of experience with Server 2003, so I'm left to figure out some things on my own.
I can tell you that I have given Everyone full control and have set the net config server timer to 9999.
I hope there are some folks out here with experience with this program. It runs most of the time, but does require a daily server reboot.