We suspect that the file has become corrupted, but before throwing it away, you
may want to try these steps:
1) Open the damaged file, save a copy under a different name, and try to use
the copy.
2) Re-install the System Software.
3) Repair the volume the file is stored on using Disk First Aid or a similar
program.
4) Since the system crashed, try rebuilding the Desktop file by holding down
the Option and Command keys while restarting.
If these steps don't help, you may be able to copy the information from the old
spreadsheet, and paste it into a new one. If you have to recreate the
spreadsheet, you might want to print copies of the spreadsheet, both the values
and the formulas (this is possible with Microsoft Excel and other spreadsheets,
and we assume it is possible to print formulas with Full Impact, too).