Note that other keys on my wireless keyboard, such as F10, seem to be working fine (in fact even F2 is working).
How do you know? Often wireless keyboards have issues at accessing BIOS setup screens before any windows drivers have had a chance to load (especially if they're USB ones and use Legacy USB isn't selected in the BIOS). Try again with an el-cheapo basic corded keyboard (just for testing purposes).
Thanks Flying_Kiwi, it worked!
But I still wonder how my previous motherboard DG41RQ, supposedly an older model, never caused such a problem? And why would some keys on ther keyboard worked while others didn't? I never expected a much advanced motherboard to fail for such a petty reason.