Have you changed the way in which you take your Power Drive? Is it a possiblility that you're taking it soon after you've had some protein?
The reason I bring it up is that one of the main ingredients in Power Drive (an amino acid) can have trouble being recognized if there are other amino acids being ingested, and competing. This is the reason it's suggested to be taken on an empty stomach.
If you haven't changed anything, then go for the Spike (you'll like it!).
But it can't hurt to take a look at how you're using Power Drive first.
Hope some of this has helped!