@Ztrucker: I have also a 2 minutes boot time in "safe mode with network" (10s less than with normal boot).
@carwiz: The diagnostics-Performance log is attached. I logged first with network connected, then not connected, I had exactly the same log in both cases, although the desktop takes 2 minutes more to appear when connected.
Sorry for a late annswer to your posts, in the meantime I reinstalled windows from a Windows 7 pro disk instead of the Lenovo disk,I had the 20s startup in the beginning, then after a couple of days of reinstalling stuffs I get the 2 additional minutes again, as expected (this is the third time I reinstall). If I look at the windows update history, the last update I have is the "Lenovo PM Device", and if I look in "restoring to an earlier time" the last installations I have are Epson WP-M4525 and Sharp MW-1800 multifonction drivers, Dell printer,VLC, Quicktime, apple software update, apple application support, gsyncit, a virtual credit card program, and updates of ccleaner, Chrome, Firefox. I am not sure if one of these caused the dealy, because it did not happened right after installation of any of these applications.
I can normally revert back to fast boot because I backed up my system drive with Acronis when it was fast (fyi, last time I backed up with Lenovo Rescue & Recovery and the restore was catastrophic, I wrote about it in another post). But I'd like to understand what is causing the delay first !