This is close. Don't know if this helps.

I was getting the some error when I upgraded to Mma9 from Mma8 on Windows 7 64-bit. It crashed right when it was initializing preferences ( as displayed on the spikey icon). (But the kernel was working fine, if I manually launched it from the start menu. I could run some calculations on it as well). I deleted the preferences folder http://reference.wolfram.com/mathematica/tutorial/ConfigurationFiles.html). Then I reinstalled Mma9. After that Mma9 works fine.

( Sidenote 1 : I checked my comp for viruses. Incidentally my comp was infected with some virus (as reported by Malwarebytes anti-malware). I removed them. I am not sure if this was the cause for this problem.

Sidenote 2 : I still have my Mma8 installed and working and this was working even when the Mma9 was not working )

This is close. Don't know if this helps.

I was getting the some error when I upgraded to Mathematica 9 from Mathematica 8 on Windows 7 64-bit. It crashed right when it was initializing preferences ( as displayed on the spikey icon). (But the kernel was working fine, if I manually launched it from the start menu. I could run some calculations on it as well). I deleted the preferences folder http://reference.wolfram.com/mathematica/tutorial/ConfigurationFiles.html). Then I reinstalled Mathematica 9. After that Mathematica 9 works fine.

( Sidenote 1 : I checked my comp for viruses. Incidentally my comp was infected with some virus (as reported by Malwarebytes anti-malware). I removed them. I am not sure if this was the cause for this problem.

Sidenote 2 : I still have my Mathematica 8 installed and working and this was working even when Mathematica 9 was not working )