Confused about GRE practice tests

[cloudwalker]

I have a question about various practice tests for the GRE.

I’ve been practicing for the GRE and I scored in the 80-95% on the Kaplan GRE and consistently well in the math/verbal practice sections in Kaplan (scores around 700 each). But when I took powerprep 3.1, I got a measly 1280! I’m really confused about this since I thought that powerprep was fairly accurate. I’m also a bit worried because this score was similar to what I scored the first time when I took the GRE. Should I worry? Or is Kaplan a better predictor?

Any thoughts on this?