When logging into Kubuntu Edgy (AMD-64) it accepts the password, starts to

load KDE but then returns me to the login screen (I had had it working fine). A console login works fine.

When I try recovery mode I get the message:
HDB (a 200GB drive) is partitioned thus:

HDB1: / ext3 1GB
HDB2: /swap linux-swap 512MB
HDB3: /home ext3 184GB

They are all formatted.

The entry for /etc/fstab on Kubuntu only has one entry for HDB and lists it as being ext3, is this causing it? With it working OK in the console login, it must be something in KDE? but I've done nothing (that I'm aware of) that would affect this. Would reinstalling KDE fix it? Is it unrelated? Please help, I've been trying to Google this but it seems people have only ever gotten it when installing the system, not after.

fstab shouldn't have entries for disks, just partitions.
If you got that far, you'd have to think it's /home that's the issue. Lets's see the output of "sudo fdisk -l" (lower case ell) and "cat /etc/fstab".