I'm admin of a Debian 6 virtual server. I've been trying to diagnose this problem for a while but haven't gotten anything. The server hangs every time I want to reboot it. All services seem to be shutting down, I lose ssh connection. Then nothing. I have to restart it through the hoster's web-interface, which just gives me the options "Normal Boot" and "Rescue System". Normal boot then brings the server back to life.

Possibly (probably?) related, the server does not boot into a newer kernel version, it's running 2.6.18 right now, but installed is actually 2.6.32.

I don't know whether it hangs on shutdown or on startup, but booting through the web-interface works (except the kernel part).

Am I missing something obvious? Where should I start looking? I have no idea how to diagnose the problem.