GNOME problem - Not able to login through draphical desktop

Hi members,
while login from the GNOME desktop ,not able to login through the graphical desktop, but while using the terminal its logging and also in terminal if i give startx then the graphical desktop comes,
i have reinstalled the gnome desktop ,
i have updated all the packages ,
atlast i reinstalled the OS also but still the problem didn get resolved… can anyone tell me what to do

Just curious:
What Linux OS are you using?..(Ubuntu?..Fedora?..Debian etc.)
You say you reinstalled the OS? were there any error in the installation logs?
What kind of machine are you installing this on? Is it “capable” of supporting the GUI?
How much RAM is installed?

hi Eddie , im using Fedora 20 , ya reinstalled the same fedora 20 only, using i5 processor and 4GB ram, it is capable of supporting GUI, previously GUI was coming , but now only its not coming… there were no error messages … can u tell me what may be the reason for this ???