Boot order changes on every start

[R4dul]

First of all sorry if there has been any similar question in the past.
I am having a really agravating problem: my motherboard's bios keeps rearranging the boot order for the hard disks on every power-on cycle. I always turn the power off at night from the PSU swith to protect from spikes. If i don't do that, the boot order remains as i set it. The problem itself is: when pc is powered on, the RAID set i use for windows and games doesn't show up at all not even in the boot device selection menu F8. So i have to reset the system and only then can i use the F8 boot menu to select the RAID and use the pc normally, and the RAID is always the last option in the list. To make things worse, the wireless keyboard i use doesn't always work on the first attempt - probably legacy USB detection glitch - but that's ok i can live with that one as long as i am able to use it in Windows.
The motherboard is Asus P5N-E SLI. Also i did verify the CMOS battery with a voltmeter and it shows over 3V so it's in good shape. Makes sense it be good since i've only had the board a few months, it's practically new even though not a new model. I also checked with Asus website for newer BIOS but not a chance, the motherboard is not even in production any more.
Any ideas anyone? Any help would be appreciated.

 

[TVeblen]

That is a problem that would be caused by a bad battery. Other than a motherboard fault there is not much else that would explain it. You might try a different battery anyway. They're cheap.

But here's a guess: check the jumper on the CLRTC pins on the MB. Make sure it is on the correct pins (1&2) and pushed all the way down.

You could try performing the CLRTC procedure just to see if it changes anything.