The first beta of the Ubuntu 10.04 development cycle has been postponed until tomorrow.
In a message to the dev mailing list earlier this evening Steve Langasek states this the reason as: -
Owing to some late image rebuilds for a couple of critical issues that we
didn’t want to leave our beta users subjected to, validation of 10.04 Beta 1
is still in progress. This means that Beta 1 will not be released on
Thursday, March 18 as planned; it will be released tomorrow, March 19.
Thanks to everyone who contacted me with this :)