Keyboard 'Lag'

Hi there, anyone having a problem where the keyboard somehow 'lags', i mean, i'm typing, and suddendly, nothing appears for like 2 seconds, i have to wait to type, or the key i've pressed will repeat like 20 times. (Very hard to write this...)
my keyboard is samsung SDK3500 : suddenly it stops working for seconds in middle of work,, sometimes it does n't work even after restarting the pc . thank you .