Blank screen on bootcamp startup

I have a MacBookPro, late 2011 version, 15" with 16 GB memory, a dual boot Windows partition, which is the default boot partition.
Yesterday, I wanted to boot into MacOS X, 10.11. When I hold down the option key to allow this to occur, I just get a blank screen, no cursor. It had worked earlier in the day.
If I let it start without trying to go to the Bootcamp screen, it starts up fine in the default Windows 7, Enterprise, after a 20 second delay.

I have looked around for similar situations, and I did not see a specific case like mine, where I can get into Windows fine but the Bootcamp option does not work.

What should I try? I should mention that this was a work computer so I do not have access to the original operating system disks, for either Mac or Windows.

Thanks much.

Welcome to our forums.

Did you try going into the Boot Camp control panel while in Windows 7 and select OS X as your default startup? If that doesn't work, try restarting your MacBook Pro by holding down the Command plus R keys in order to get into recovery. Then use Disk Utility from Utilities to run First Aid on the hard drive. And by the way, there are no disks for OS X and haven't been since Snow Leopard 10.6.8. Everything is a download from Apple.

I tried a few things that I found online and flashing the PRAM seemed to be the one that allowed it boot directly into Bootcamp. I had not tried this earlier thinking that I had to be booting into the Mac side of the partitions, but it seems to have corrected my problem.
Thanks for your help.

Boot up and hold down Option and all drives available will be displayed and take your pick.

harryb2448 said:

Boot up and hold down Option and all drives available will be displayed and take your pick.

Click to expand...

This was my original problem as when holding down the option key at boot gave a blank screen with no cursor. After a minute or so, it would then boot into Windows (the default boot partition), via bootcamp.

I do need to make a bootable dvd or usb thumb-drive.

Flashing the PRAM [ hold down option, command, R, P at initial power-on ] has seemed to fix this problem for me.

Make a bootable flash drive. You will need an 8gb flash drive for the installer. Follow these instructions, https://support.apple.com/en-us/HT201372