It seems that unicode has broke MDX somehow. The only way to fix this it for DragonZap to get out of his layer and update it :-) heh
Yes that's right. Now it s*x for people using MDX for many years. As we know DragonZap has not updated his files for a long time.
Coming back to the selection problem in an editbox I found the problem. mIRC gets the color from Windows item named Selected Item. And then we have a black background and Selected Item's color is also black what results in not seeing the selection. It was not like that in the previous mIRC version.