On 12/22/06 all Yahoo support received a support-wide message that support will not be working on manual imports. (If you send them a file attachment to be imported into your account, it's not going to get done and you are not likely to be informed)

When sending uploads or file attachments, some clients, not all, are having a problem with their .csv files being converted to a form of zip file (.gz). Some Yahoo staff are smart enough to re-save the file and open it, some are not. In any case, if it's a file for manual import they wont touch it anyway. If this happens to you, the file CAN be opened. Instruct them to simply re-save the file, select all file types and select the .csv. Presto, a file that can be opened in excel.

Yahoo support seems to be very, very, swamped.

Google bulk downloads can be directly uploaded/imported into Yahoo Panama via the built in conversion feature within your new Yahoo account.