I had this problem for the longest time with bluetooth and 8.04.1 on a different Dell Laptop. I found no help either, just one day it started working. I figured an update must have solved whatever the problem was.
I'm assuming that by "generic" Ubuntu you mean not Dell's custom install but your installation.
I'm not sure how to fix your problem (if it isn't already solved) but I can give you two pointers. One is that even if you don't have the Dell's pre-installed Ubuntu, Dell's Linux support will still help you out if they can quite cheerfully, or at least that is my experience.
The other is that when I was having my bluetooth issue, I was always able to pair the mouse to my machine with a command in the terminal. Clearly this isn't a permanent solution and you have to do it each time you boot up the computer, but it worked for me at least until the problem "fixed itself".
In a terminal type:
sudo hidd --search
Enter your password when asked and make sure that the you've pushed the pairing/search button on your mouse. This usually makes the indicator light (if you have one) blink on your mouse. If you run this command while your mouse is in that searching mode and give the computer a few seconds to find it you should get connected. It has at least worked for me without fail.
I hope you find a better solution than that, but if not I hope this command works and is helpful in the meantime.