Kate, have a look at the following:
If you have given the exported file the extension ".csv" and you double-click it, Excel will open it as if it were an Excel file, and it will look for TABS that seperate the fields.
However, when you export a file from Cardbox, the character used for seperation is the COMMA.
But, when you import the file in an empty Excel sheet instead of opening the file directly, you're asked which character seperates the data: TAB, semicolon, comma etc.
You can import the file using the 'Data' menu in Excel, or change the extension of your exported file to ".txt" and double-click it.
Make sure you select "comma", otherwise Excel will again look for TABS. Excel will now recognise your fields.