Swap partition mysteriously disappears

[Derek Broughton]

Does anybody have a clue how/why a swap could quietly disappear?

Fairly often (enough that I'm going to put a "swapon -a" in the resume
sequence after hibernation) it happens when I hibernate and resume -
there's obviously a valid swap partition at hibernate time, but it doesn't
get reused after resume.  This makes sense, as I understand swsusp changes
the partition's signature and it isn't actually a valid swap partition at
boot time.  otoh, when this happens, "swapon -a" always works.

At other times though, I'll be working along merrily until suddenly the
system freezes as the disc thrashes.  In this case, "swapon -a" works about
90% of the time, but occasionally I have to "mkswap" the partition. 
There's never anything in syslog to indicate a problem.

This appeared to start after I installed boinc, but I can't see any obvious
clue - except that boinc is fully intended to try to maximize resource use,
so could be filling the swap space. 

It happens with 2.6.15-25 and all 2.6.17 stock ubuntu kernels.
-- 
derek