I finally got the answer from Apple. Their Engineering department provided the following...

"Scanning networks can add time to the picker process, depending on the number of networks found. There is no way to turn it off. Only MacBook Air and newer Mac mini support this feature."

So if like me you have one of these 2 Macs and there are a lot of wifi networks nearby then it will take a long time to boot and there is nothing that can be done about it.

Hi,
the same problem for me, I installed Windows 7 and Mountain Lion with bootcamp 4 on my mbp mid 2012 with SSD using rEFIt (I also tried without bootcamp, first)

after the rEFIt choice, the system waits about 90 seconds on a black screen (with a blinking cursor) and then windows starts quite fast, normally

I noticed this problems appeared during the windows 7 installation. The first boots to the installer were quite fast, and after x reboot during install, this black screen appears each time..

I've updated all the windows drivers with bootcamp support (I only had a msg that tells me that the usb 3.0 drivers couldn't be installed properly)

any ideas ?
thanks

manu

same black screen a startup for me, I found the solution :

if for some reasons windows didn't recognize the installed version as genuine, you can use the tool windows_loader made by Daz to fix the problem. I used version 2.1.7 and it works well with bootcamp.