I was sent a SharePoint taxonomy that had been edited in Microsoft Excel. When I attempted to import the taxonomy I received the error “Not all terms were imported successfully. Please see the server log for more information”
When I looked at the csv file in Excel I couldn’t see anything wrong with it. However, when I opened the file in Notepad++ http://notepad-plus-plus.org/ the cause of the problem was obvious. If you look at the screenshot below you can see that editing the taxonomy in Excel has added extra rows to the csv file which are invalid.
I used Notepad++ to delete the extra rows, see below. The taxonomy then imported without error.