Hm, so it isn't just me !
This kind of problem is very disconcerting for newbies, and annoying for anyone. I'm quite used to partitioning now, but because of the potential for damage, and because I don't do it nearly as often as comparably fundamental tasks, I still try and keep things as simple as possible. For that reason, I haven't got very far yet with command line tools, even though I imagine they are simpler to use once you're used to them.
The great attraction of GParted is its ease of use, so this is something of a blemish. It's worth thinking that for anyone who is really new to Linux, Gparted is the first thing they'll see after a live CD. When you consider that many people in that situation are going to want to dual boot with Windows, which is trickier than a straight Linux setup, any (even apparent) difficulty around partitioning constitutes a serious bottleneck.
Gparted did something else unnerving this time: I had an (empty) data partition on sda5, and Salix on sda6. I wanted to change the filesystem on sda5, and probably should have reformatted; but instead, I deleted the partition and recreated it as ext4. Gparted then reported it as sda6, with Salix renamed to sda5 - but still the rightmost partition on the drive. Lilosetup then wouldn't work, and I suspect the partition table had become faulty. Indeed, when I reinstalled Windows on sda1, Salix disappeared! I was easily able to fix it using parted, but it was an unnerving five minutes, because I had some data on the Salix partition I hadn't backed up - namely, my backup image of the Windows partition on sda1!
Perhaps the moral of the story is that if you back up properly, there is no reason to be at all nervous about altering the partitioning scheme.
