Liteon 5006 picture jerk or freeze

please please help me with this problem.i used a recomended disc to record off sky,but when i play back the finished program i get either jerkiness or frozen pictires. i then tried recording off freeview which also ended up with the same problem,i emailed the company who instructed me to update the firmware which i did, but i still get the same problem. anyone having the same problems or has any answers please feel free to reply or should i just take it back to the shop. :a