I've seen other threads about this (yes, I did do the courtesy of searching first before I typed this 
but they all seem to be about external drives.
One of my internal drives (it doesn't even have anything on it yet!) often (but not always) gives a warning that it was not ejected properly after I wake up my computer from sleep. Not only that but it doesn't show up in Disk Utility either. If I restart, it comes back.
I am running a MP 5.1 with Mavericks.
Perhaps relatedly, the computer will seem reluctant to go to sleep. Sometimes it will act like it is going to sleep and then wake up again quickly. Attempting to put it to sleep again sometimes does nothing. I'm not sure this has anything to do with the disk problem though.
but they all seem to be about external drives. One of my internal drives (it doesn't even have anything on it yet!) often (but not always) gives a warning that it was not ejected properly after I wake up my computer from sleep. Not only that but it doesn't show up in Disk Utility either. If I restart, it comes back.
I am running a MP 5.1 with Mavericks.
Perhaps relatedly, the computer will seem reluctant to go to sleep. Sometimes it will act like it is going to sleep and then wake up again quickly. Attempting to put it to sleep again sometimes does nothing. I'm not sure this has anything to do with the disk problem though.