channels are freezing with fun card

Hello all ,
I am so very new in all of this and i would like to get to know what I have ..
all what i want is to open up the channels of Hotbird/Arabsat.
I have a starsat 3500cuci .
I have bought the fun card , but everytime i watch multivision or france 2 or france 3 . the picture freezes every 2 minutes and i have to wait .
Also , every time i want to switch chanels, it takes so much time to do so .
WHY ?? Can you please help me knowing the problem ??
and if you need me to check the software or firmware on it , please tell me how to do it .
I also need to buy the cable from my computer to the satellite ,. what kind of cable should I buy ??
Thank you :)