I have just installed InDesign CS4 trial for Windows (normally I don't use this program, but I needed it to test my OpenType layouts) and was very surprised with the following odd effect: when I am attempting to stack several combining marks over a base character, they are lined up diagonally, each subsequent mark higher and further to right than the previous one. Thus the vertical positioning is correct but the horizontal is completely wrong. I have an impression there was just a typo somewhere in the source code, so that marks are shifted by the same amount of space both vertically and horizontally.
The problem can be reproduced with any font (e. g. SIL Doulos) and any combining marks for which proper mark to mark attachment points are specified.
Now I am wondering, if anybody else has experienced this problem, and if so, if it is known to Adobe developers?