XLS file open 2 – 5 times on W2K server

I have a WinXPSP1 Pro networked to a Win2KSP3 server. Excel Files are stored on the server in a shareed folder. When I open an xls file in ExcelXPSP1, make some changes, then try to save I can’t. The file is not read only. The Open Files on the server shows multiple xls files of the same name open, but I only opened it once. Why is this happening? The file was originally created in Excel 97. The files still show up as open on the server even when I have closed them in Excel. This appears to haven randomly.