Half fps in standalone than in editor

I am using Unity Pro 3.1 in a Windows XP PC.(AMD X2, Geforce 285GTX, 3Gb Ram)
My problem is very strange. I get 30-35 fps in my project in the Unity editor but when I build a standalone or Web Player (same quality settings in all cases) I only get 12-15 fps.(in the same machine of course). I post this a few weeks ago but the problem persist and nobody can explain it.
Please, any idea from Unity team?

Is the editor quality set to the same settings as standalone/web? Other than that, we can’t possibly know what the problem is without checking the project.

Yes always same settings…is very rare.
The problem has to be related with Unity building process not my project or the computer because I can run very modern games in that computer ( I have played Mafia 2 in high settings) with good framerates.

I read your old thread, and did a web search, and found no good answers. I was wondering if the problem occurs in every Unity project you run, or just the one you are working on ? Have you tried to make a different project and see if the run times are affected ?

I have tested other projects and I get similar results, maybe not so low fps comparing with the editor but always less framerate (20-30%) in the standalone than in the Unity editor. I thought it was just the inverse…

PD: I get always the same fps in the standalone regardless of the screen resolution or quality settings !