My kid's machine did that. Eventually the maker issued a new bios and now it seems fine. As we can't fix a bios you have to ask Dell if they are going to issue a new one that addresses your issue.
The theory is that the BIOS is looking for bootable devices.
I got a external USB hub for my Dell Vostro Desktop (note: I bought the HUB BECAUSE of this problem so I dont think its the case) and I admittingly do plug a lot of USB in, but lately when I start the computer up, at the initial 'Dell Screen' before windows loads it gets stuck there and stays there.
The solution to get it to start is to unplug the usb hub (which has 4 things plugged into it) and then it will start up and I re plug in the hub after windows loads.
I have to do this EVERY time, why would USB be causing this?
USB things I have hooked up:
2 USB External Hard drives
A Mouse, A keyboard
A game controller USB receiver
Now I guess its kind of a lot of things, but it should be able to handle 6 usb connections right? I also notice sometimes the ipod through USB data transfers VERY slow.
Its like its getting overloaded, any way to fix this?