Only native resolution available

I am using Intrepid x64, up-to-date on a Dell Inspiron 1720 (geforce 8600m GT, 180.22 driver). My problem is that though I DO get the native resolution from the screen of 1920x1200, I cannot select any other resolution. And I also suspect that something with the dpi is wrong, as for example in the log-in screen the font is somewhat badly proportioned (the dots in the password field are slightly larger than the field itself for example). In hardy I partially solved the problem by adding some modelines to xorg.conf, but this does not work anymore in intrepid. Anyway, I am just wondering, is the EDID firmware of my monitor itself garbage or might there be some other cause to the issue? It remember it working on windows when I got the laptop, also, trying with ddcprobe I get edidfail (although ddcprobe is said to be deprecated and only reading EDID version 1). The issue does not seem to be tied to the proprietary nvidia driver - same problem using the opensource version.
Just in case, here are the EDID bytes of my screen:

EDID BYTES:

0x 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

    ------------------------------------------------

00 | 00 FF FF FF FF FF FF 00 32 0C 00 E4 00 00 00 00

10 | 00 11 01 03 80 25 17 78 0A 56 35 9D 5A 52 8F 27

20 | 1F 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01

30 | 01 01 01 01 01 01 60 3B 80 A0 70 B0 23 40 30 20

40 | 36 00 6F E6 10 00 00 19 60 3B 80 A0 70 B0 23 40

50 | 30 20 36 00 6F E6 10 00 00 00 00 00 00 FE 00 52

60 | 50 36 31 36 00 31 37 31 57 55 31 0A 00 00 00 FE

70 | 00 1E 2D 37 3E 5A 77 A3 FF 02 01 0A 20 20 00 8E

Thanks!
smani