After shutdown for a few days - black screen when booting

[zimon]

I shut down my FreeNAS for a few days and when I started it again I was not able to connect to any of my web interfaces. Also SSHing into it was not possible.
So I plugged in a monitor and keyboard and I saw a black screen with a blinking cursor.
When I restart the FreeNAS after the bios when the boot process starts the black screen with the blinking cursor appears again.

I have my boot usb drive mirrored but even when the drive is dead, shouldn't there be something like "can't read boot device" be displayed?

What should I do?

 

[Jailer]

Replace your boot device(s), reinstall and upload a copy of your saved config file.

You do have a copy of your config files saved correct?

 

[zimon]

I solved it, for some reason there was another bootdevice selected in the bios. How can that happen?

 

[MrToddsFriends]

I solved it, for some reason there was another bootdevice selected in the bios. How can that happen?

Maybe a firmware bug. Would you like to tell us which hardware (motherboard) you are using?

 

[Redcoat]

Could you have chosen a temporary one on the previous boot?

 

[zimon]

I did not mess with the boot device at all.

I have a HP Proliant Microserver but I cannot tell you the exact motherboard (I don't have access to it right now)