Easier said than done, I'm afraid...  We're working from a customized version of your 6.1 source code.

 

I did compare the Safari Loader from 6.5 and the one we had from 6.1, and there were no substantive differences in the loading code, so I'd expect it to have all the same problems with Ext.

 

Ext does a lot of weird things with divs on their apps that appear to be messing with Safari 4 and how Cute initializes...

 

We do use Cute with Safari 4 in non-Ext apps and it seems okay.