Merge & Center only applies to last group of cells selected...

I have no clue what caused this problem...

Whenever I select multiple group of cells using CTRL (say B2:D2, then B3:D3, then B4:D4) and click on the 'Merge & Center' button on the ribbon, it only merges the last group of cells I selected (in this case, B4:D4). The other two groups are still highlighted as selected, but don't merge. It is working however if I use the drop-down arrow next to the 'Merge & Center' button, and use the 'Merge Cells' option...but it is very annoying.

Any idea what may be the cause of my problem, and how to solve it ?

Thanks.

I looked through the options, I don't see anything about merging... :/

Thanks for taking the time to take a look, appreciated.

Anyone else ?
I guess re-installing could be an option, but I would hate to go through with that only to find out it was a simple checkbox hidden somewhere.

Yeah, it works just fine whenever I use 'Merge across' or 'Merge Cells'. Even once they are merged, if I click on the 'Merge & Center' button to un-merge the same selected groups of cells, it works.

But 'Merge and Center' to actually merge multiple different groups of cells doesn't work, eventhough it used to (and should). And I have no idea why...and it's been that way for all of my workbooks, so it's not specific to the one I'm running test on right now. :/