Wrong partition ordering
If you have a hard drive with two or more logical partitions in one extended partition and then proceed to erase the first of those logical partitions (in GParted), then you will soon discover that the number of the second logical partition changed (from sda6 to sda5 in my case). If you then try to create a partition in the free space and launch cfdisk, you will notice that there is no free space where it should have been. If you then manage to get to GParted and create a partition there, then do not relax, as your perils are not yet over. Upon reboot you will find that the logical partition that is in the beginning of the logical partition got a new number (sda7 in my case) and the your valuable second logical partition is still numbered wrongly (it was sda5 instead of expected sda6). Even more so, if you try to fix it with cfdisk, it bails out with a fatal error of overlapping extended partitions.
The fix is to start fdisk, press "x" for advanced operations and press "f" to reorder the partitions according to the order on disk (do not forget to enter "w" to write the changes). That fixed the problem. But I have no idea who to bug for this wonderful Mongolian Clusterf*ck of Partition Numbering.
And that is only a tiny preview of the immense fun I am having right now by trying out installations of Debian etch and Ubuntu edgy on my Dell M1710. If you want a stable desktop on this computer right now - use Ubuntu Dapper (with nvidia binary drivers). You will have much unneeded fun with IPW3945 wifi and the NVidia video card drivers otherwise.
Edit: fixed fstab -> fdisk. How silly of me :)