Game Lag - Jumpy

Hey All.
I am up to level 17 but finding the game tends to have a big lag - play starts and stops, very jumpy.
At times the game continues but jumpy and I am unable to move the cursor.
Has anyone else found this?
Is just my computer?
How can I get the game to run smoothly?
Makes achieving gold very difficult.
Any help much appreciated.
Cheers.