Betfair has been experiencing technical difficulties since about 9am and have turned off API access whilst they restore services.
Whilst the API remains turned off, you will not be able to log in to TBE.
Unfortunately we are at the mercy of the Betfair engineers to restore services and turn the API back on.
Updates are given out via the Betfair twitter account - @BetfairHelpdesk (http://twitter.com/BetfairHelpdesk)
Alistair