There is a problem with recent kernels (I think to recall 2.6.20 as the first to tail) and Thinkpads wakeup behaviour.

Please read the following problem description twice as many people seem to misunderstand my problem:

After the first (successfully) suspend to disk using swsusp from the vanilla kernel waking up from suspend to ram using the LID button fails. Waking up by pressing the Powerbutton still works.

Even /proc/acpi/wakeup tells LID is enabled for wakeup:

$ cat /proc/acpi/wakeup
Device  S-state   Status   Sysfs node
LID       S3    *enabled
SLPB      S3    *enabled
(...)

It actually is not. There is a small workaround; just disable and reenable LID as wakeup source:

echo LID >/proc/acpi/wakeup
echo LID >/proc/acpi/wakeup

And maybe find out why swsusp fiddels with these values. After rebooting wakeup works out of the box

Edit(2007-07-16): Does not work reliable.