Am fairly sure its your usb drivers, Ive had untold problems with them and even had DELL's finest stumpt for a week, finally ffound these and problem went away never to return
firstly find your error code by doing this
1.Restart your computer.
2.When the Dell logo screen appears, press F12 several times to open the One-Time Boot menu.
NoteNote: If the One-Time Boot menu does not open, wait for the Windows login screen to appear. Then restart your computer and try again.
3.Use the Down Arrow key to select Diagnostics (or PSA+ or Enter ePSA), then press Enter to begin the assessment.
4.Write down any error codes listed on your screen.
5.Use the Dell Interactive Support Agent to get information on the error codes listed in the PSA.
cold start from floppy, would leave the broadcom till last, you can put all these on a floppy or rewrite dvd or usb stick just remember to F2 it frond cold start and tell it to start from usb, floppy or dvd
I hope this is helpful, nothing worse than having a dead beauty sat next to you