When I turn on my laptop, it's a Lenovo W520, everything seems to work just fine but after the Windows logo and before the Desktop loads I get a black screen for about 30 seconds, and after that the desktop loads and everything is ok. I can only see the cursor on the black screen before the desktop loads. It does not affect anything, it is just a bit annoying that it boots into windows but does not load the desktop.
I can even take a screenshot during this 30 second window of time. I have uploaded the zipped boot trace file here