I'm not Husse, the email you get for topic reply notifications just happens to come from an address of his
It might help to clear the air; the current version of X used in mint 8 does not require an xorg.conf at all
with xorg modules (there appears to have been a move to zero config). If a modified xorg.conf is causing issues, an easy step is to simply remove it.
Further, it might help to completely remove the nVidia driver you have installed since it is not for your card. You can do this through synaptic since you obtained the drivers using it.
If you are able and willing, a clean reinstall might the safest route of all, as it will achieve the above two objectives as well as resetting any other configuration settings which might have been altered in the meantime.
On a similar, slightly later gen 9600 radeon there is no problem setting resolution at all; however, if after reverting to the default radeon module and absence of xorg.conf it remains impossible to set resolution, it might be worthwhile starting a new thread about that. Best of luck to you and thanks for being patient.