Gigabyte motherboard - two DIMM slots got disabled somehow - help!

[redstang]

I have a Gigabyte P55-UDA3 motherboard where 2 DIMM slots have become disabled. I made no hardware changes and have been running this computer with all the current components for years. I have 8GB in four 2GB memory DIMMs, one in each slot, and for some reason two of the slots appear to be disabled now. I will include a pic of the current status screen from my BIOS setup. In there you can see that it can tell that 2GB sticks are installed, but the slots are not enabled. Also, Windows recognizes that there is 8GB installed, but states that 4GB are "hardware reserved". I will add a screenshot to show this as well.

My question is whether or not this means the motherboard went bad, or if there is something that could have happened to cause those slots to become disabled (like an OS update or something odd) such that there is some way to enable them.

Things I have tried:
Rotating the memory DIMMs into different slots: No change, all the DIMMs appear to work fine.
Check the 'maximum memory' setting in the advanced boot options in MSCONFIG: It is unchecked.
Installed different video card: No change. Thought maybe the memory on the video card went bad causing the computer to reserve memory for that, but again, no change.

When searching for posts related to this issue, all I found were instances of this happening to people that were installing their memory and/or OS for the first time. Not the case for me - I have been using this computer for 7 years, and have been running Windows 10 for two years with all 8GB available. Windows did recently perform an automatic update, but I am not sure of the exact date that this issue happened so I'm not sure if it was ok before the OS update or if the issue happened after.

CPU: i7 870k
Vid Card: Radeon 5780
Windows 10 on Samsung SSD
6 other HDDs installed

Any advice is appreciated.

 

[jankerson]

Set bios back to defaults.

 

[redstang]

Set bios back to defaults.

Thanks - but I also had already tried that (forgot to put that in my list of things I've already tried). I actually updated my bios to the latest version as well. Still flummoxed as to why those slots aren't enabled. Seems very odd to me that the motherboard would just go bad in this way.