I have been billing a client for quite awhile with no problems. The last time that I did this the invoice appeared ok but when I looked in the summary the (contact) name was different. I do not see any where in Paypal where a customers personal name is listed or how it can be changed. I am wondering if that comes from the customers end.
It could come from the customer's end as they may possibly have updated their name. You can check the Address book in the Manage Invoices page under Settings menu. Also ask the client if they have recently changed their name. If the invoice has not been paid yet, you can edit it if needed.