I was about to compose this question around the problem that my USB 2.0 ports had suddenly become USB 1.1 ports and solicit ideas on troubleshooting. Then I discovered that a reboot "cured" my problem!
To be specific: I have a laptop (Dell Inspiron 1420) with Win 7 ultimate that I have had for quite a while. I regularly transfer files via flash drive. Two days ago, for the first time I got a notification saying: "This device can perform faster if you connect it to a Hi-Speed USB 2.0 port." Checking device manager I observed 5 entries for "Universal Host Controller" and 2 entries for "Enhanced Host Controller". One of the latter group had a warning icon; looking at properties it said it was disabled because it was not functioning properly. I read one article that said I should start by checking BIOS settings so I needed to reboot. Though I did not really find in my BIOS what the article claimed should be there, it turns out the reboot was all I needed. Now device manager shows no warning and when I plug in my flash drive it no longer gives notice about using a slow port.
So---at the moment--I do not seem to have an issue but I was hoping someone might be able to shed light on why this would happen, is it likely to happen again, and how does one troubleshoot it?