A strange thing I have noticed is the following. When booting Windows 7 x64 on my Thinkpad e520, right after the "Starting Windows" screen (glowing windows flag) my screen goes blank for 10-20 seconds typically. It is not a black screen but as if the screen is off. After 10-20 seconds the logon screen appears as normal and everything works normally. Note that this does not happen every time I boot... sometimes it is off for a quick moment and the logon screen appears. This is how other laptops I own and have worked on boot with Windows 7.
This is a clean install of Windows using the latest drivers and BIOS available on the Lenovo website. I have tried using the latest graphics driver from Intel's website and the same thing happens. Disabling all non microsoft services and startup programs (a clean boot) does not resolve the issue.
Unintalling the graphics card driver in device manager or booting into safemode solves this so it seems likely to me that it is a video driver issue.
note: After investigating further I've noticed that this issue doesn't happen until after I apply the first round of Windows updates after a fresh install... perhaps there is an update that is causing this?
Here is a video of what happens. The audio can be ignored (the beep is not from my laptop).
I understand that this is the point in the boot process where Windows initiates the video driver... on other machines I have there is a brief period of the screen being off. On no other machine have I seen such a long pause.