Bluetooth dongles caused me more hassle than any other single piece of hardware, I'm guessing you're not on Windows 7 as bluetooth installation was a breeze for me on W7. You can try:
open device manager
find the bluetooth device (I'm guessing it is an unknown device in device manager)
right-click it and choose update driver
browse my computer for driver software
let me pick from a list of device drivers on my computer
hopefully you will see the driver you installed before the reboot listed
select it and click on next, hopefuly the dirver will install
The problem I used to have on XP and Vista was that microsofts own bluetooth drivers would get installed, and the vendor drivers would just get ignored, the steps above should remedy this if this is your problem. Hope this helps.