What am i doing wrong?

Have just got a canon 40d & 70-200 f4 l usm lense,which i will be using for mainly motorsport.Been going through the different set-ups ie basic shooting & creative zone modes.My question is in basic "sports" mode camera and with lense set to "af" i get continuous shooting as says in manual no problem,but when i set to "tv" shutter-priority,al-servo & high-speed continuous shooting (want to practice "panning),when i press shutter all i get is 1 slow "click"! what am i doing wrong? any help on this would be great. Mark

Since you're in shutter priority mode, I have to ask, what's your shutter speed set to? Sounds like it's set to something low.

Have you been experimenting with mirror lock up? That gives you one click...

The penny has just dropped:o,i had been on mirror lock (you know what its like,new toy and i wanted to go through all the sections,but hav'nt a clue what i'm doing!) and did'nt go back to "disable," have now and creative modes working fine,thanks a million MintMark! Mark

Thanks Dorsey for your reply,canon forums are great for help etc.Problem now solved and camera working perfectly.