USB ports provide power but do not recognize any USB device

The 4 USB ports on my Dell Inspiron 9200 (running Windows XP Home SP2) no longer recognize any USB devices attached. This started occurring after my computer refused to come back from Standby Mode. I eventually forced the computer out of Stand By mode by clicking the power button and typing on the keyboard at the same time.

I then attached my Maxtor 4 Mini USB External HD and noticed that my USB ports no longer recognized devices that were attached. However, all devices are provided power through the ports, and all of the devices work on other computers.

I tried the following to help resolve the issue:
1. Attached Mouse, provided power but did not recognize the device. Hardware wizard does not even come up.
2. Attached 3 USB flash drives to each port and they were not recognized either.
3. Uninstalled all USB Root Hub Devices and rebooted. No change.
4. Uninstalled all USB Controllers and rebooted. No change.
5. Installed a logitech mouse driver which is the same as the mouse installed. Mouse was still not recognized.
6. Re-flashed the BIOS. No change
7. Ran Dell Diagnostic utility and no issues found with the USB ports or controllers

I'm at a loss, and do not know what to try from here. I'm wary to think that the ports are dead as they are still providing power and the no diagnostic is finding a conflict or issue with the ports.

Does anyone think that any of the following things have any merit?

1. Replace the HD with another HD and see if the USB ports are working with the new OS on the new HD?
2. Backing up all files and reinstalling the OS?

Please provide any suggestions that you have for me, I really don't want to reinstall the OS, but if that is my only option then I'll have to do it. Thanks in advance.

Hiya. I work in IT support and recently saw a similar problem happening with our HP workstations... In fact, after trying quite a few things we realised that if we unplugged the power for a few minutes, and plugged it back in again - the USB ports mysteriously started working again. We've managed to narrow it down to one USB external hard drive which was somehow 'short-circuiting' (for lack of a better word) the USB ports. Hope this helps somewhat, but I don't have an explanation...

I had this problem on a customers Inspiron 1720. The fix for this machine was simply enabling External USB in bios. It was set to off but was able to power my mp3 player. Good luck.