TSM BA Client Password issue

All,

I am having this strange problem, the other day our tsm server was brought down for an upgrade and offline for 24 hours, once it came back around 50 % of client backups missed because of password issue. I've checked couple of client config, In them schedmode is set to polling and CAD is not configured. Is this the problem? I don't understand it quite, Can anyone suggest anything?

Thanks