I have a 2008 Mac Pro that boots to a flashing ? folder icon. I cannot boot into Recovery. I can boot into the Startup Manager by holding the Option key.
In Startup Manager, a configured hard drive with OSX 10.11 installed is available, the Recovery partition of that hard drive, and a separate OSX installer on a USB. When any of these boot options is selected, the computer then freezes on a gray screen.
I've tried the PRAM, NVRAM resets, the SMC reset, switching drive bays, etc. Any help would be appreciated!