Made my day! Now, our E5420 don't crash coming out of standby. 
We have to redeploy some machines now..
Thanks Marco!
At first try I got an error:
2014-04-10 10:48:57, Error DISM DISM Driver Manager: PID=396 Failed to install the driver package 'C:\Drivers\win7\x64\security\R308120\Drivers\tcwbfadv.inf'. - CDmiDriverStore::Import(hr:0x80070002)
I found out that this is some kind of fingerprint reader driver, which is not built into our devices. I zipped these drivers so dism won't try to install it. How do you handle this kind of errors? Simply add it to the successful return code list in the template? Or is there a dism switch to prevent the installtion of devices that are not present?
EDIT: One more question: What about devices, for which there are no Windows 7 drivers available (on the Dell Driver CAB download page)? Do you create a dummy folder which contains one hardware independent driver, so that the action won't fail?
Regards,
Carlos