Runtime error of '2501' with multiple users when saving

[BobS]

Recently installed a small Access (2003) application for a non-profit association which I wrote on my home pc. Copied the database to a share volume and the Access mde to another shared volume with a short key set up for it. Application starts up fine and user is able to key in records (forms using data entry property), access current data via another form and modify the data on the form. A save record button was created for the user by using the Access command button feature from the tool bar. Everything works fine with one user but if we have multiple users, when someone makes a change and hits the Save Record button, a "Run time error of 2501" is generated. It doesn't seem to matter what the other user is doing. Looking at the VB code generated by Access:
Private Sub cmdSave_Click()
On Error GoTo Err_cmdSave_Click

DoCmd.DoMenuItem acFormBar, acRecordsMenu, acSaveRecord, , acMenuVer70

Exit_cmdSave_Click:
Exit Sub

Err_cmdSave_Click:
MsgBox Err.Description
Resume Exit_cmdSave_Click

End Sub

Any suggestions? Looking at other "2501" posting, I don't see anything similar.

Thanks for your help,
BobS