windows 2000 and shared excel sheet

HI Again! We are using a shared Excel worksheet for tracking calls and times in the call centre. Everything is working 100% until we installed Windows 2000 on one machine. Whenever that workstation tries to save the shared file it is not saved in the proper file but it actually changes the file to a 0 kb file and saves the spreadsheet elsewhere on the drive in a non-excel format which can still be read by excel. Any thoughts?