BetsyR87,
If your mail acct has a webmail interface, make sure that there is not a
large message in your inbox there. Or some SPAM message that is corrupt, and
blocking the download. I have had a few messages in the past few days, which
I believe contained Russian words in the subject line, that had to be
deleted, before the download could complete.

Delete the obvious Spam through the webmail interface, and maybe create a
folder there and move, the messages from the inbox, into it. Then place back
some of the messages into the WebMail Inbox. Then close the webmail, and
restart Outlook, and see if the download will complete. You can then go back
to the acct's webmail, repeat the process with a couple messages at a time,
until you find the one that is causing the problem. You may have no choice,
but to delete the message, because its too corrupted to be received by
Outlook. Or you might try to forward the message as an "attachment" to
another email account, that you have Outlook set, to get mail from.

Hard to say without any configuration information. My guess would be that
your virus scanner is causing this. If you have a virus scanner that
integrates with Outlook, disable this integration and try again.