Modified by template

Hi,

We're using a large (9Mb) EXCEl spreadsheet in a busy networked environment. We only want to have one person update the file at a time, though we need to know who is currently on the file. If you open the file when another user is on, Excel usually tells you that the file is being "modifed by USER do you want to open as read only or be notified when it becomes free" More often than not, it is now informing us that the file is being modified by TEMPLATE, even though we know a legitimate user is in the file. Why is it doing this and how can we force it to give us the Username of the individual rather than displaying template???

Additional Notes: This problem is NOT user specific i.e If I open the file, it will tell everyone that it is being modified by myself, though on other occasions when i have the file open, it tells users that it's being modified by TEMPLATE.

Please help.