Reading related posts it seems I have a blend of other's issues. But the final blow was plugging in a nextbook tablet to download some pdf files, and THEN I booted the old Mac Pro 2008 with Yosemite 10.10.3 or 4, can't recall exactly now since I can't check it. I 'assume' having the tablet plugged in on boot confused the boot up sequence?

I've tried every startup key configuration in the official Apple list, except trying the few 'over the internet' options i.e. 'Option-D: Apple Hardware Test/Apple Diagnostics over the internet,' 'Command-Option-B Start up from OS X Recovery over the internet,' because my hardwired modem is on the computer I'm using to get help. I'll power this down and try it now, but if that doesn't work, which isn't likely, it's still in White Screen Hang. It was also black screen crashing before this and restarting over and over, intermittently... if that may be contributing to this issue. Thanks.


Already tried NVRAM reset?

I've been surprised by how many problems this "fixes": https://support.apple.com/en-us/HT204063

Turn on your Mac.

Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.

Hold these keys until the computer restarts and you hear the startup sound for a second time.

Release the keys.

  • Thank you, Jaime Santa Cruz. Yes, I did, but I think I did it incorrectly re: the holding and sounds. I'll be able to try this again Wednesday, and I'll RSVP. Thank you so much!
    – suz
    Aug 18 '15 at 1:34
  • Jaime Santa Cruz: I was able to get to this tonight and unfortunately it didn't work. I did it twice, just to make sure, and the 2nd time, the HD started whirring way fast/loud, so I power button powered down before it blew. It had done this for me a couple+ times before when I was trying different things. So, I'm still getting the Apple logo, progress bar goes about 1/4 to 1/3 across, then stops, white screen, with the pointer up in the upper left corner. Any idea why plugging in a nextbook tablet would do that? Seller told me I could download pdf files from my Mac. ? Thanks.
    – suz
    Aug 19 '15 at 2:39
  • gah, formatting fail....let's try that again... Had to go find the site again, but I thought I remembered there being offline diagnostics options: (from support.apple.com/en-us/HT201255 ) Shift Start up in Safe Mode. D Start up to either Apple Hardware Test or Apple Diagnostics, depending on which Mac you're using. Command-R Start up from OS X Recovery. (this one may not help much, but I think I remember there being some "repair" option in there.
    – s1ns3nt
    Aug 19 '15 at 14:38
  • Jaime Santa Cruz: Thank you. I'll try those again. After I tried many, I even printed out the 'Startup key combinations for Mac' official list from Apple Support, and tried them all again, except the ones that required the internet connection, which I'm using now to get help from AD/you. I ended up with white screen hang, but I will try the above again per your suggestion. Then,I'll have to change internet connection and try the Option-D Startup AHT or AD over the internet... BUT I won't know what to do once I get there unless there are instructions. Thanks!
    – suz
    Aug 19 '15 at 18:45
  • Where did my comment go? Trying again: Thanks. That's the list of official Apple Startup Key Combination for Mac I printed out after trying some I found elsewhere. Then I went thru the entire list again, except the ones requiring internet connection, which is on this machine, obviously. I will try the above again, but if I get into the AHT/AD, or even OS X Recovery, I won't know what to do. I'll connect the internet to the MacPro2008 with white screen hang and do the Option-D and Comman-Option-D over the internet and see. The MP2012 I'm on now is for sale.
    – suz
    Aug 19 '15 at 18:51

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