I had to fix a couple of problems with Debian unstable while updating today. I'm not sure if these are the right ways to fix them, but they worked for me.
wibble::exception::System' what(): No such file or directory.. Searching led to bug #472695. Seeing that it was a problem with a dependency on debtags, I tried
apt-get install debtags and sure enough, that made aptitude happy again.
Installation of linux-image-2.6.24-1-686 was failing with a grube-probe error, "grub-probe: error: Cannot get the real path of `/dev/sda'". I found that in grub's
device.map file, there was an entry for
/dev/sda. I have no idea why, since I have no such device on this system. Removing that line and re-installing the package fixed the error.