Your Q is not properly clear here! USB ports related to what, USB printer / USB flash drive.... Does the OS identifies the devices, Click Applications>Accessories>terminal and type as: fdisk -l (if u want to mount flash drive) and observer if it shows the drive.
Even u can type lsusb and see what devices are listed for usb. Try to see Places>Computer and if the USB device is there, then it simply not mounted. In that case, type as: mount /dev/sd* /mnt (here * means last character of the device, replace this with this one)
If it related to USB printer port then look at this:
https://wiki.ubuntu.com/DebuggingPrintingProblems#AppArmor%20Protection%20of%20the%20printing%20system

Also check ur BIOS / CMOS setup for disable / enable issue.

Type in sudo mkdir /media/mydevice in terminal. Then, after a few seconds, type in dmesg | tail. Look for sdb:sdb1, after finding it, type in sudo mount /dev/sbd1 /media/mydevice. Note: if you find, say, sdb:sdb2,for example after using dmesg | tail, then replace sdb1 to sdb2.

Sorry if I'm wrong, I'm still a novice trying to find their place.