Reopened Excel file after a crash, can't be opened a 2nd time

I'm using a 2008 MacBook Pro, running OSX10.6.8 on a 2.6 GHz duo core processor and using 2008 version of Microsoft Excel. Can't recall if that software has been updated on line or not, but I don't think so. Not sure MS does that for Apple users.

I've used spreadsheets extensively for over 25 years, and often work on fairly large files. Apart from the sadly far too frequent crashing of Excel when I use large files, I have not had difficulty using this equipment and software for the last 5 years. Over that period, Excel file crashes have happened to me dozens if not hundreds of times, so I am familiar with all the standard fixes for Excel files that have crashed.

Recently I created an excel file from scratch by copying pasting and reformatting about 1000 records from 20-30 different files. At one point the file crashed, so I reopened it and saved with a different extension and continued working on it. In saving it I eliminated the "version 1" part of the extension that comes up on a recovered file. After continuing to add records to the file for another hour or two, I closed it and shut down my work for the day.

The next day I was unable to open the file and got an error message saying it may have been "damaged or modified from it's original format".

I have tried all of the tricks I know - renaming the file, going back through a number of different possible extensions, etc and still cannot get the file to open. Other Excel files in the same folder open easily. Only the one I was working on won't. It took me several hours to compile this file and I'd rather not have to recreate it. I am looking for specific detailed information about what might help me recover it.

I searched for an answer to this query on line and found a person at Microsoft (XinXin Liu) who worked in the Excel for Mac Group there, who had responded to this kind of query at least as recently as April 2012. According to his messages to that group, he had users send him files that wouldn't open, then "fixed" and returned them. I see from LinkedIn that he is now working for Apple and hope to hear from him. If you know how to contact him, please send him this message. Thank you.