One for the archive:
I have a monowall that said "swap_pager_getswapspace: failed" every time I 
wanted to see the firewall states.
The particular monowall is old, has been upgraded to each new version, and 
there were some leftovers in the xml. In particular it had:

<diag>
  <ipv6nat>
    <ipaddr/>
  </ipv6nat>
  <ipfstatentries>30000</ipfstatentries>
</diag>

When there's 128MB in the box, mono bumps its head. With 160MB it's slow, 
but does succeed.
A rough calculation says it allocates about 3k for each entry it's asked to 
display, regardless of wether there's that many entries.

/Kasper Pedersen