I need help with MDX TreeView Control and mIRC 7.49

For some reason TreeView Control is not correctly triggering mouse clicks, except if I right click it, then it generates an sclick event but nothing happens if I click or double click it.

I know my code is correct because it works in mIRC 6.35 but I need to use 7.49 because of UTF8 in 7.49 works better than in 6.35 ...