BOB91:
The adapter output voltage is 6.5 V it should be higher?
If you're connecting that to the Arduino's power socket so that it is brought down to 5V by the onboard regulator, the minimum voltage required is about 7V. See the Input Voltage section on this page:
http://arduino.cc/en/Main/ArduinoBoardUno
If you supply less than 7V then the nominal 5V output may be less than a true 5V which can cause things to misbehave.