export product data from Opencart

Hope you can help.

I am trying to export the complete product list so I can make some changes in excel and reload the data once changed. I have used this for ages and all of a sudden I have tried to export the product list and its coming up as corrupted.

I only get one page of data rather than the spreadsheet with 6 tabs of data I have had in the past. The excel program is telling me that the file is not in the format it says it is and when I open it up it reads rubbish.....

Is anyone else having this problem?
is there a way I can fix it?

It's possible that your OpenCart inventory has become too large for the export tool to handle, so it is not completing the file.