Your USB question fails to provide key information.
1) Do/have these USB ports worked with other devices under linux?
2) What kind of drive are you plugging into USB ports (ie: flash drive or external hard drive, etc)?
3) Have you tried at least two different devices/drives on the USB ports?
Is this a brand new drive, or have you used it on other computer?
If this is an external hard drive, be sure to flip the power switch on the back of the drive (commonly overlooked by users).
I suggest you make sure the 'hotplug' system is running. To see if it's currently enabled/running, check for the existence of the /var/lock/subsys/hotplug file with the following command (and post the output here):
ls -l /var/lock/subsys/hotplug
To enable hotplug, make it's startup script executable and reboot, as follows:
chmod 755 /etc/rc.d/rc.hotplug
If after doing so, you still cannot mount and access your USB drive, display all the partitions which are visible to linux with these commands:
Be sure to post the output of those commands here so we can further help you.
Also, be so kind as to post 'exactly' all the commands you are using to try and mount your USB drives, and manipulate them, etc (also include any output, error messages, that sort of thing).
If any of these resolve your issue, please post details so others may benefit as well.