Suspend to ram doesn't work after Feisty upgrade

[Mariano Draghi]

Hi,

After successfully upgrading to Feisty, I couldn't get my laptop (Dell
Inspiron 640m) to suspend to ram anymore.

Suspend to disk works (most of the times, not always... but it has
always been like that)

But suspend to ram NEVER works, and under Edgy it worked 100% of the
time.

With Feisty, whenever I try to suspend to ram (either by lid-close,
Fn-Esc keyboard shortcut or Gnome power button), the laptop seems to go
to sleep (the screen blanks, and the power led start to blink), but
immediately (after a couple of seconds) it wakes up again. Then a
notification from g-p-m informs me that my system couldn't suspend, with
no further information and/or reason :(

How can I debug this? I was searching through launchpad, and
there are plenty of bugreports on suspend issues, but none seems to
describe my problem. And I'd like to get some more information about the
problem before opening a new bug.

TIA,

-- 
Mariano Draghi