CSV Compatibility between Windows & Mac

I am trying to use the Bulk Up-loader Spreadsheet' template provided by Bid Or Buy (like eBay) to upload a large amount of items for sale. It is a CSV file which was created using Windows. I have a Mac running Microsoft Excel Mac 2011. Simply opening the CSV 'scrambles' all the data as Windows & Mac handle CSV's differently. The file needs to be imported into a new Worksheet first (delimited) and then displays correctly enabling me to edit the data. The problem is that when I then save the file in a Windows CSV format and upload to Bid Or Buy I get the error "The number of fields in the CSV file doesn't correspond with a supported version of the Trade Bulkloader". Logically thinking it is because I need to save it in a format that looks the same as it did before I imported it (scrambled on a Mac). How do I accomplish that?

Thank you