Where did you install the IDE? Where is your sketch directory?
On my computer, the IDE is installed in:
C:\Users\PaulS\Documents\arduino_1.0.5
and my sketch folder is
C:\Users\PaulS\Documents\Arduino
If you followed any kind of similar scheme, it means that you have a copy of the Servo library in your libraries folder that conflicts with the one that comes with the IDE. If you tried to install the IDE in the sketch folder, that isn't going to work.