I'm having some recurrent problems with the merge/unmerge function using 2d square icons.
First, even with the 2d, I would say that I have to repeat the select/left-click/point to map region/un-left-click sequence 2 to 5 times probably about 50% of the time. I have no idea how the grahics-mouse interface on something like this works, but I would not say that mine is running well. It really takes away from the enjoyment of the game when you have to repeat a command multiple times to get it to actually execute. It could be that I have a problem with non-updated drivers or something like that. If there is anything I should try to update remind me how to do that, and I'll be happy to see if if fixes it. Or if you need a DxDiag or whatever. I'd like to do whatever I can to help you to get it fine-tuned so it works well on a variety of within-spec machines.
A related problem, that seems to have become more common than when I played the game before (maybe before patch 1.06a) is that: I select a corps to either move in or out of an army in the same region and instead of just that single corps merging or unmerging, TWO of the corps in the same initial detachment will merge/unmerge.
Say for example, I have the German X Army in Konigsberg with three corps in it (XL in reserve and XXIII, and XIV not in reserve . . . just hypothetical, I do not remember the actual units involved, and I've had the problem recurrently for virtually ALL armies and corps in the extended CP alliance [Germ, AH, Ital, Bulgar, Turk), and also lets say there is one other German VIII detachment in Konigsberg with two corps in it (XIV and XXII).
The problem is happening in two different ways:
1) I select XIV Corps and try to merge it with X Army. Instead of only XIV Corps merging into X Army, BOTH XIV AND XXII Corps will often merge (but not always). Also, a lot of the time when I try to separate XIV and XXII into two separate stacks, it either does not work or it merges them in a way I did not tell them to merge.
2) Lets say I try to remove (unmerge) one of the corps inside X Army, say for example XXIII. I select XXIII and send it to the map region, but instead of only XXIII unmerging and forming a new separate stack, both XXIII and XIV will unmerge.
In sum, about as often as the merge function does exactly what I tell it to do, it does not do exactly what I tell it to do.
If you want I can give you a series of .savs with exact details.