cubase sx timing problems

[the19thbear]

hi.. i´m using cubase sx ( not 3,0 or 2,0, the old one ok!) and i´m inserting the xtc delay plugins as i´m told to in the scope manual, but i still get latency/timing problems..
i have, lets say 8 channels of audio, and load a xtc delay compensating plugin into each insert channel, then i take track one, wich has vocals on it, and add the sfp compressor plugin, to adjust the sound of the vocals.. and listen to the track along with the drums playing to tracks2,3,4,but a tiny bit of latency occours(the vocals used to be in perfect sync with the drums, but not after inserting a compressor etc etc..).. i tried updating my plugin information etc etc.. but it deosnt work.. there is still latency/timing problems. anyone else experienced this??? thanks