folder permissions

I need someone with some experience in file and folder security on NT 4.0

I have the following set up.

My Documents on a NT file server Shared with Everybody having change permission.
The Security on this folder and the files in the folder have the following settings. There are four groups the Read/Write group, Read group and two groups with full control.

My question is I may have a user try to access an Access db and that get a message saying this file is already is use; couldn’t open. What’s wrong?

Thanks,
FREC