Alpha texture went wrong!!

It went horribly wrong and horrible!!!

I use a box with <0,1> taper to look like triangle. My texture has alpha it in and only half of the texture is displayed on the prim. But now in 1.10.1, it went wrong in the most horrible way!

The whole texture suddenly applyed to the Triangle without my command! And the worse, When I move camera around it seem to flicking back and forth between 1.10.1 look and the new wrong look! Do i have to say how horrible that make my whole building look now???

Anyone else seen this?

I want 1.10.1 back now!!!! I can't stand seeing at the stuff anymore!