This worked for me. Since I am on Vista,
http://forum.ppcgeeks.com/showthread...ght=bootloader
I was going to roll back to XP to do this. But it worked as Helmi said immediately after the RUU driver load.
http://forum.xda-developers.com/showthread.php?t=304408
I will say this happened to me during the WM6 upgrade, but I got it to flash and still stuck in boot loader. Now it is loaded and running fine