Excel 2004 filed spreadsheet will not open

I cannot open many of my filed excel worksheets. I select file, defaults to Excel, select open and the spreadsheet starts to open and then closes. I have tried going back and restoring the file from my time machine and the same thing happens. I have tried selecting open, other, and then selecting excel from applicationsin finder.I am using excel 2004.
If I start a new worksheet I can close and open without any problem!!
PLEASE can some one help and need access to some of these worksheets urgently.
many thanks, Chas