Are you using a USB hub or are you connecting the iPad sync cable _directly_ into the MacBook Pro?
Have you tried using a different USB port?
Do any other USB devices work? E.g. do you have a USB mouse or USB keyboard you can plug in or perhaps a USB memory storage device?
Are you running any virtualization software (VMware, Virtual Box, or Parallels) that might be intercepting the USB device?
Go into Finder and open "Applications" -> "Utilities" -> "System Profiler"
In System Profiler select the "USB" category from the list on the left (under the "Hardware" section... they are listed in alphabetical order so it should be the last entry under "Hardware")
On the right you should see the "USB Device Tree".
If the iPod/iPhone/iPad was not _already_ connected when you started "System Profiler" you will need to select (from the menu-bar at the top of the screen) "View" -> "Refresh" to get it to to re-scan the devices on the USB bus.
You should see the device in this list.
If you do not see it, you might want to contact AppleCare for support (if covered) and/or make a Genius Bar appointment. They have a hardware test utility which is much more comprehensive than anything provided to consumers (e.g. Apple provides a "Hardware Test" on one of the disks that comes with every new Mac but it's not very comprehensive and I don't think it'll test USB.)
