I just heard that something has gone awry with the switching on of the backup system on Hubble. It's not clear what's going on as I write this or how serious it is, but Hubble has gone back into "safe mode" which is when it shuts itself down and awaits new orders. NASA is planning a telecon on this at 3:00 Eastern time. I unfortunately won't be around to listen, but it will be webcast on their site.
I'll post more info as I find it.