I'm having the exact same problem, and I also have an Inspiron 1150. I literally just went to use my USB ports one day and they'd stopped working. Based on what I've been hearing, I'm going to try to figure out this whole 'new PCI card' thing... which may take some time because I'm a tech novice.
Just a few things to add (maybe with a few more clues, someone out there can figure out what exactly happened... assuming that it was the same cause in both cases):
1. NONE of my devices are working, and they include: printer, external keyboard, mouse, CD burner, hard drive, and iPod. And sometimes a flash stick.
2. I tried the whole uninstall root hub thing in the device manager on my own. When I rebooted, Windows seemed to be able to detect that there were drivers that needed to be reinstalled for all my devices even without any of the actual devices being plugged in. The driver reinstallation process seemed to start on its own (I think.... forgive me if some of the things I say sound dumb or don't make sense). EACH installation process got hung up before it completed with an error message like 'incompatible' something and just terminated.
3. I have an optical mouse, and it's still getting power- I see that the light is on on the bottom of it!
4. I was on the phone with Dell support for 2 hours- the dude tried all sorts of crazy stuff but then said the next thing to try would be "reinstalling" the "operating system" and that that would "ERASE" my "HARD DRIVE". I said no thanks... I didn't feel spending loads of time loading ALL my files up to the internet.
5. Final thought- wasn't there a windows patch that was issued in late November/early December 2008 for some sort of security thing? Is it possible that messed something up with the USB ports on Windows XP? Maybe just for some people? I'm asking because as I've been searching through posts of people with problems similar to mine, it seems as though there were a bunch posted in mid-December.
Thanks for reading my ramblings. I know I am verbose.