No Object In This Control

Hello everybody.
I have an Access application with a browse button that allows to search for files on computer. It does not work on all computers.
Computer A and computer B both are running XP Pro and Office Pro 2003.
Browse button works on A but throws ".. no object ..." error on B. It also works on a computer running Office 2002. Office was uninstalled [typical] and re-installed as full install on B and that did not fix the problem.

Here's my browse button code.

Private Sub cmdBrowse_Click()
' Prompts user for back-end database file name.
On Error GoTo Err_cmdBrowse_Click
Dim strFileName As String
Dim oDialog As Object
Set oDialog = Me!Xdialog.Object
With oDialog ' Ask for new file location.
.DialogTitle = "Please Select New Data File"
.Filter = "Access Database(*.mdb;*.mda;*.mde;*.mdw)|" & _
"*.mdb; *.mda; *.mde; *.mdw|All(*.*)|*.*"
.FilterIndex = 1
.ShowOpen
' If user responded, put selection into textbox on form.
If Len(.FileName) > 0 Then Me![txtFileName] = .FileName
End With
Exit_cmdBrowse_Click:
Exit Sub
Err_cmdBrowse_Click:
MsgBox Err.Description
Resume Exit_cmdBrowse_Click
End Sub

So, what's the difference between my A and B? Does it have to do with Activex controls?

Any help would be greatly appreciated.
Thank you.