Excel cell protection

I have an excel spreadsheet that was first created back in 2001 by a third party. We have recently moved from Office 97 to Office 2003 and I now find that a number of cells in the spreadsheet are suddenly protected when I open it in Excel 2003. If I open the sheet with 97 it functions fine. If I try and unprotect the sheet I get asked for a password, which I don’t have. Has anybody come across anything like this and have any thoughts ?