No, I don't mean the kind my grand children are using at the beach in South Carolina, but the ones you get to see when your Mac takes some time to load a program or complete a task. My Mavericks setup which worked like a charm until about three days ago is now broken. The computer kept crashing regularly since that time. It clearly has to do with Parallels. It corrupts the windows image file. I restored it twice, after which it worked for a while. But then Parallels corrupted the image again. I believe this problem has to do with a recent update, but I don't know. Information about what got updated when in Parallels is scarce on the Internet. I have Version 10.2.1 (29006). One of the error reports mentioned Kekst signing, Apple's excuse for "security."
In any case, I have had to revert to Yosemite and can't use SSD.
Needless to say, I am not happy!
One day later: The problem does not seem to be caused by Parallels, after all. The crashes continued in Yosemite. The likely culprit is USB 3.0. Others are having those problems too. After disconnecting all USB drives, I have not had a crash (in a few hours).
1. But see here.