How to clone HDD to SDD using Disk Utility?

I'm trying to copy the data on my HDD to a new Crucial M4 128GB SSD, which I would like to replace with my HDD. The HDD is still in the MBP and my SSD is connected via USB by a external SATA controller.

I'm trying to clone the HDD using this solution:
https://discussions.apple.com/message/15260335#15260335

I've set my Source to my Toshiba drive and selected my SSD for the destination. When I press the Restore button I get this error:
Restore Failure
Could not validate source - error 254

Does anybody know why I get this error? I have tried to restart in Recovery Mode and use Disk Utility from here. Still same problem. I'm running Lion.

 

I'm wondering why Disk Utility says that the partition is using 50,38GB whereas CCC only copied 42GB. Why? I choose the "Maintain a backup" option. Was that right?