regression suspend/resume on Lenovo T420

Hi,
I'd been sucessfully running CURRENT on my Lenovo T420 with functional 
suspend/resume since some time. But after updating to CURRENT r317032 
respectively r317559 suspend/resume does not work anymore. Putting it 
into suspend results only in a black screen, but no further action is 
possible (only pressing the powerbutton for some time to switch it off 
completely). The LEDs are not indicating any suspend mode.
If i try to suspend it with X (intel-driver) stopped, the laptop does 
switch into suspend, but does not resume. It runs into some kind of 
resuming endless loop, where it tries to start the laptop again but at a 
certain point it restarts again. The screen stays dark all the time.

I tried this with and without the following options but the same result.
hw.acpi.reset_video=1
dev.acpi_ibm.0.handlerevents='0x04'

Booting a Bootenvironment with an older CURRENT(r315141), all is 
working.  Was there any change between these commits concerning 
suspend/resume?

BR
Manuel