My chat window would crash as well with the latest update on beta, but a user fixed it for me. The only change he did was change some sounds from "ui_pressed" to "sounds/button" and add the page "ChatShadow":
<Page BackgroundOpacity="0.200" Location="20,99" Name="ChatShadow" PackLocation="nfn,fff" PackLocationProp="0020/0001,0006/0001" PackSize="absolute,fixed" PackSizeProp="0017/0001,0002/0003" ScrollExtent="297,17" Size="297,17"/>
I suppose it is that page that needs to be there.