Are you currently using LDAP account or an admin account? The admin account should work fine the LDAP though could run into this issue if your computer rebooted (it should clear up in about an hour).
What happened is when your browser came back the UCSM "application" would have detected an inconsistent state where you were logged in but had a different than expected cookies. After about an hour it will perform a cleanup of the stale session (hence the prompt to wait a few seconds) and then you would be able to login.
You could clear the cookies manually or use a different browser if you did not want to wait.
- Please mark posts that are helpful or have solved the issue so other members can find them more easily.