Major Bug? Edgy 'losing' swap file

[Chanchao]

A week or two ago I had major instability problems, lock-ups and so on.
Turned out that Edgy somehow lost it's swap file. 

I then reinstalled everything from scratch.

Now I have the same thing again it seems.  I just got another lock-up,
and upon rebooting and checking System Monitor it shows me Used Swap: '0
bytes out of 0 bytes'. 

I'm VERY positive that it had swap upon reinstallation, because I
checked!

So how does this get lost?   And more urgently, how to I tell it to go
use the swap partition?

Cheers,
Chanchao