Nokia N73M
Sofware hanging

I brought new nokia N73Musicedition mobile on 2 month back

Fulgently software has been hanging on standstill condition. Two times i formatted the memory card and one time updated the software.

Still the problem has been coming. What is the solution?

is there any problem for using the mobile cover?

i came to know that the processor speed is reducing while using the cover

is it true?