Delayed response to keyframes

Hi guys,

I’ve got a particle system with animated speed values. The speed will stay constant and then spike briefly before continuing as normal.
According to the IPO curve editor, there are three speed spikes that occur for the particle system within the first 80 frames.
However in the viewport and when I render, the particle system is vastly delayed. I rendered the first 80 frames as a test and the particle’s speed only spiked once!

Has anyone come across this problem before? What am I doing wrong?

(Let me know if this isn’t clear enough)