Importing Address Book

I have copied my Address Book from my ibook (OS 10.5) to my imac OS 10.4.11), however I cannot seem to then import this information into my Address Book on my imac. The message i get is "the file you selected does not appear to be a valid comma separated values (csv) file nor a valid tab delimited file, please choose another file."

Can anyone help otherwise I'll have to type in ALL the details again and I'm sure there must be an import option that I've missed!

have you selected all recipients in your address book and exported as vcards. If you didnt, do this, then copy to your iMac address book

Address book in Leopard (10.5) is different from Address book in Tiger (10.4), and as with other software, NOT backward compatible - ie, you can import your data from 4 to 5, but not the reverse, as you wish. I think that's your problem