Some of the scenarios where incorrect child count is read - might need to document if it is Win 7 specific issue.

TreeView:

Launch Ensemble
Using Down Arrow go to Child Node 3 and try to navigate using Up, Down , Left, Arrows
Hear what the narrator says, sometimes 0 and 1 children. When navigating from the child node 4, 5 using the up arrow it is aware of the correct children count as 5
 
Prefer to keep this bug open for doc purposes, if it ends up to be a Win 7 only issue and is not going to be fixed.