I had errors like this when using super agent repositories at remote sites. reason was that at night the vpn connection was droped (and I guess in the middle of repository replication process) so the clients at the remote site did's find a valid repository (or only mcafee.com). Could it be sth like this? (btw: when selecting "show files" from ePO at one of these repositories, I got errors too).
If you use a UNC repository, the ePO server (the user you entered) needs to have write permissions