BIOS hard drive not present

[thufir]

On boot, I get a message that hard drive hasn't been detected, then I 
press (I think) F1 to continue and the boot continues.  Mounted devices:

thufir at dur:~$ 
thufir at dur:~$ mount
/dev/mapper/ubuntu--vg-root on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/cgroup type tmpfs (rw)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs 
(rw,noexec,nosuid,nodev,size=104857600,mode=0755)
none on /sys/fs/pstore type pstore (rw)
/dev/sda1 on /boot type ext2 (rw)
systemd on /sys/fs/cgroup/systemd type cgroup 
(rw,noexec,nosuid,nodev,none,name=systemd)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse 
(rw,nosuid,nodev,user=thufir)
thufir at dur:~$ 



history:  on this same computer, a little bit ago I was in a different 
account and tried to switch accounts from 13.10 unity, but got a black 
screen with a blinking underscore cursor.  When that didn't change after 
a few minutes, I tried REISUB but only the B for boot worked.  The other 
commands, or at least the first few, gave an error that the SysReq wasn't 
allowed -- which is odd, because I've use REISUB on this pc before.

In any event, in the BIOS the boot sequence showed **nothing**, by which 
I mean (as I recall) "not present", something like the screenshots at:

http://superuser.com/questions/338360/why-is-the-usb-device-option-not-
present-in-my-dell-optiplex-bios

so I went into discs and turned "on" all the sata, pata and IDE options.  
On reboot, I was able to boot into Ubuntu, as described above.  With some 
trial and error I can go back and turn "off" some of those drives so the 
boot sequence is smoother.  (I was just blindly turning things on at the 
time.)

My concern is:  does this indicate failing hardware?  Loose wire?  It 
seems odd that BIOS would spontaneously not register a disc it saw 
previously?  Is there a connection between the odd black screen from 
switching users and the BIOS??



thanks,

Thufir