Has anyone experienced reboot problems recently?

I have a U2 where "shutdown -r now" shuts down the machine, then it says
"rebooting" on the serial console, but doesn't do so. I have to power it down
and up again to get it back to live.

This never seems to happen on my other machines (U5 and U60).

Martin

P.S.: of course OF does not respond in that state either