BeforeSave Cause Crashes

I have the following code that (should) either save the file with a generic name if a value exists in a certain field, or else save the file as the contents of the value in the field, with a message box appearing in either case. The problem is, the message box appears twice (not once) and then Excel crashes! Can anyone tell me what's going on? The code is:

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Dim FSR As String
FSR = Range("I7").Value
If FSR = "" Then
MsgBox "Service Report Number not entered."
ActiveWorkbook.SaveAs Filename:="Service Report Navilas.xls"
End If

If FSR "" Then
MsgBox "This action will save the file as the Service Report Number."
ActiveWorkbook.SaveAs Filename:=FSR & ".xls"
End If

End Sub