i haven't looked into this in detail, if the USB ports worked fine before the windows 7 upgrade I would check the lenovo web site for any windows 7 specific drivers or even vista drivers or other info for this problem........ I needed specific drivers for other issues on newer thinkpad models for retail windows 7 installs/upgrades.
Sounds like a driver problem to me...........and you can check your hardware drivers via the device manager and system profiler.
If USB 2.0 continues to be an issue other then an extensive repair (motherboard) a PCMCIA USB adapter would be an inexpensive solution.