Travelmate 7520G 2400xt -> 4650 DDR2 (MXM-II upgrade)

Hello everyone,

I just got my hands on a HD4650 1GB DDR2 [VG.M9606.005] for my Acer Travelmate 7520G (MXM-II) to replace the HD2400xt.

1) HD2400xt 2) HD4650


When I booted I only got a gray/white screen and the GPU/CPU fan didn't even start spinning (it didn't even let me see the POST screen.. nothing).
I tried using the DVI and VGA ports with an external display, but nothing seemed to work.

Is there anything I could do, or is the card just plain broken?
Some (hidden) BIOS options to change or maybe flashing a modified one to allow HD4650 to work?
I read something about a corrupted MXM-Structure and .NetRolller 3D fixing it to work with the 9600M GT but I doubt this would help me, because I couldn't find an edited BIOS for Travelmate 7520G..

I'm using Phoenix BIOS 1.17 (25.3.2008) ( Bios on Acer's support site seems to be dated to 12/08/2008 but it won't start the flash program (POM117.exe) under win 8 64 "Open Flash.sys Fail")
Edit: Apparently the same BIOS applies to the following models:
Extensa: 7120 and 7420
TravelMate: 7220, 7220G, 7520 and 7520G

I've browsed most of these forums but haven't found issues with Grey/White screen of deaths (GSOD?) nor solutions.

At the moment I have my 2400xt installed and the laptop is running fine with upgraded Arctic Silver Ceramique thermal paste (max temp 65C when gaming) but I'm looking forward into upgrading to HD4650..

Thanks for reading and I hope there is some kind of solution for this.