serial port greyed

Hello,
My arduino 2009 / IDE 0021 don't recognize the usual USB port anymore
and "serial port" remain grey!
I looked at "troubleshooting" and also download again 0021 and but no
result.
Could someone help me?
Thank you in advance

Operating system ? Its probably thats where the problem lies

Windows vista (sorry!)

Does the arduino com port show up in device manager ? Any yellow exclamation marks or red crosses etc ?

I have the same problem. Have Windows XP SP3. Can i make it work?

No, only "peripherique USB composite"
What should I do ?
Thank you anyway for your help!

Assuming it doesn't have an exclamation mark next to it, it could be the Arduino, ideally you need to try the arduino on another computer and/or another Arduino on the same computer. Depriving it of power (shut it down, pull the plug from the wall and remove its battery if its a laptop) and then restarting it may have an impact.

I load again a driver and now COM LPT line is there again and also
a yellow exclamation mark!
Windows says: pilot is correctly installed but...problem code 34;
any idea again?
Thank you in advance

Maybe try a different USB cable or USB port on your computer? Or try it with a different computer to try to see if the problem is the board or the computer.