The update basically worked. But now something with the nameserver is broken. My resolv.conf is empty and i can't resolve names although i do have basic ip connectivity. Need to investigate this ...

I'll keep documenting this here, just in case someone runs into the same issues. I have tracked this down to the point that udhcpc creates a resolv.conf in /tmp/resolv.conf.wlan0 whereas dnsmasq expects this file to be in /var/run. Copying the file manually fixes the problem.

Does anyone here know how the file is to be put into /var/run ? The first few lines of the file responsible for this look like this in my machine:

Is this file broken on my machine? Should this really read /tmp in that RESOLV_CONF line? Can someone confirm this?

Edit: Further down this thread you'll find the solution. Here's the short version:

The problem is due to the fact that i some time ago had vpnc installed. The vpnc installation modified the file /etc/udhcpc/libicd_network_ipv4.script (and left it in that state after i uninstalled vpnc). The update wants to update this file, but since it recognized it as not being the original version doesn't touch it. Instead the new version isbeing saved by the update under /etc/udhcpc/libicd_network_ipv4.script.dpkg-dist

So the solution is simple: get root (e.g. sudo gainroot) and do a "mv /etc/udhcpc/libicd_network_ipv4.script.dpkg-dist /etc/udhcpc/libicd_network_ipv4.script" to replace the old modified version with the one the update tried to install. After that everything is fine again.

This also means that you probably shouldn't install vpnc on updated machines before this has been sorted out.