Keys function/ Navigation key not working

Dear Friend,

I have this I-Mate Sp5m, I am in love with my new bought device, but I wonder what went wrong and its keys have become slow.

The worst thing is the navigation key.

1. Press down function is not working anymore
2. On scroll down the key is performing 2 functions together
a. scroll down
b. and press down

The no 2 problem is making me go crazy as I cannot navigate on my phone. If I need to scroll through contacts, I cannot control the speed of scroll and where ever I stop the key second function comes in to play and I am taken a step further.

Please please Please help me fix this problem.