Currently Being ModeratedMar 5, 2013 6:09 AM (in response to veedeekay45)
Software you reinstalled after reinstalling OS X over itself is likely outdated.
Some programs place a at boot kernel extension file and if it doesn't work, then it causes the gray screen issue.
You can cause these to not load by holding the Shift Key down while booting up. Then uninstall the software with their uninstaller, then reboot normally, then getting the software updated which will work with your current OS X version.