I own this wheel as well. Have had not problems at all.
You might should check that all of your power is at proper voltage. You could also have a problem with the USB port you are plugging into. Is it one of the front USB ports on your computer or one of the back port? In all case i've seen the fronts are an extension from the boards USB pin out. These could, because of the length/quality of the wires inside the computer cause a power issue and power issues can cause odd computer behavior.
Here are a few things to check on:
are you using any USB hard drives/cd drives on your computer? The self powered type can eat a ton of power from your USB bus.
Are there a lot of USB devices connect at the same time?
Are you plugging the wheel into a USB hub instead of directly to the computer?
Do you have a USB extension cable on the wheel? Note: i have had weird problems with cheap USB extension cables before.
Have you tried the wheel on another computer?
can you see the voltage monitor and if so are volts in operating range of the computer? I you need a motherboard monitor try this one it is free: Motherboard monitor 5:
http://www.majorgeeks.com/download.php?det=311
I do not have those extra mice/keyboards installed on my PC with this wheel. Are you using a laptop by chance? Those can have up to 2 pointing devices installed (touchpads and/or small joystick in center of keyboard).
Lastly. If all of the above check out I would see if you can return it to the store or where ever you purchased it from for another. Remember Logitech doesn't support this wheel on the PC so if you have to return it I would try and stay away from mentioning use on a PC. Play dumb and just say it doesn't work.