dhclient: format_min_length(h): No safe value for unknown format symbols.

The version affected is dhcp3-client 3.0.4-12ubuntu

I'm getting that bug too, but it says on mine that there are 7 extra bytes instead of 6.

This is with the "ifup" command after the network has been previously shut down, and a prior terminal window brought up.

and your network interface is configured to use DHCP?

This looks like a regression from this change:

dhcp3 (3.0.4-12ubuntu2) feisty; urgency=low

  * Add debian/patches/dynamic-hostname.dpatch:
     - Add support for a new string type 'h' which behaves like 't' except
       that '<hostname>' is changed to the current hostname.
     - Change 'host-name' DHCP option type from 't' to 'h'.
     - Based on a patch from Nathan O'Sullivan, thank you!
  * debian/dhclient.conf: Enable send-hostname by default (value '<hostname>',
    which our shiny new patch from above will translate to the actual
    hostname). Closes: LP#10239 and two handful of duplicates.

http://pastebin.ca/374339

@Ralf: Yes it is.

 dhcp3 (3.0.4-12ubuntu3) feisty; urgency=low
 .
   * debian/patches/dynamic-hostname.dpatch: Fix a few forgotten places where
     the new string type 'h' must be handled as well. (LP: #87816)
   * debian/control: Set Ubuntu maintainer.

I *think* I caught everything now. Feedback is appreciated though, because I was not able to replicate the problem.