Outlook sending error

I seem to have a bad email stuck in the sending process. Each time I click
"send/receive" I get the same error message. However the send of new
messages to my stored Outlook contacts does succeed and they are received.

My computer is a new Vaio with Win 7 and Outlook 2008, and outlook contacts
transferred from an old computer with XP and outlook 2003. Everything worked
for a month until I manually typed in an email address for a new email. The
error occured whenI clicked send/receive. That message seems to be stuck
there and creates a new error each time I send/receive any new email.

error message: Task – Sending� reported error (0x80070057):
“Could not complete the operation. One or more parameter values are not
valid.�

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Frank