Yeah when they say that Ubuntu 6.06 recommends 256MB+ of RAM to install they are not joking. I was trying to install it on a Dell Optiplex GX110 and it ran like a dog. The intaller died on the partitioning step (looks like the /dev entry didn't appear). So I deleted the partition table and rebooted. This time since there was no handy swap partition it ran like a very sick dog.
Insert a 128MB DIMM and it works like a charm. I never checked the RAM when I started - it would be a nice feature to write in large letters somewhere at the start of the installer "YOU HAVE THIS CPU, RAM, FREE SPACE" etc. Oh and when did it get so hard to match RAM to a PC? It took many attempts to find a working DIMM (eventually canabalised from an old Optiplex GX110). I'm sure back in the 386 days any RAM would do :)