Have you tried it with one servo?
Are you providing an external power supply for the servos? The Arduino is not able to provide enough power for more than one SMALL servo. They won't move and the Arduino is likely to hang up.
When you reply, include the sketch you are running. Use the "#" button above your text and put the code between the code delimiters.
A schematic of your Arduino and servos or at least a photo of your setup would be helpful.
When using multiple servos, you must supply power to the servos from outside. Outside power goes into the Renbotics servo shield at the green screw terminal. Read the owners manual and make sure you don't get the positive and negative wires backward or you may be replacing a lot of equipment.
John