Hi Chris,
This is an strange issue. Here are some things you can check on:
1 – for a user with the error, browse out to the C:\Users\[username]\AppData\Roaming\Microsoft Dynamics SL\ folder and delete the APC folder. Then login to SL and try again
2 – Try going into “all users” customization level and try again. Maybe the user with the error has some other self level customization that is causing a problem.
3 - May also want to look to see if there are any other “group” level customizations on that screen that could maybe be causing the error.
If both screen customizations are doing basically the same thing, then I wouldn’t think it was some missing component or DLL or whatever that the non-admin users didn’t have.
Let me know what you find.