can't activate swap partition in 3.4

I installed 3.4 on HD, everything seems to be working fine. During the install config, it can recognize my swap partition ok, and even tell me that it will use it as swap.

But after booting it, there's no swap. If I try to run swapon command, I get

swapon: /dev/hda1: Invalid argument

From dmesg, I see the following error msg:

Swap area shorter than signature indicates

What does that exactly mean? I had tried to remove the swap partition with fdisk, and recreate it, and still get the same error.

Current config:
- IBM thinkpad T30
- Knoppix 3.4, kernel 2.6

/etc/fstab :
/dev/hda1 none swap defaults 0 0
/dev/hda2 / ext3 defaults,errors=remount-ro 0 1
...

This machine was working just fine with 3.4. I installed 3.4 on another desktop machine, and there's no swap either. But the desktop machine does not have the error msg in dmesg. No other messages, swap is not activated, and can't be activated manually. WTF...

Forget about it.

The knoppix installer somehow does not format the swap partition. Fixed it with mkswap.