It already was the case with the beta of zDesktop 2, both on Seven 64 bits (french) and OSX 10.6.3 (french).
I've upgraded to RC1 this morning (on Seven only for the moment).
Sync went well.
But, still nothing happens when clicking on any of these buttons (New Mail, "Reply", "Reply to All", "Forward").
I've forced zDesktop to US english (instead of french) without success.
When using "Always compose in new window", I'm getting something strange : the new window opens, starts to fill itself but stops before fully filled. And result is broken :
. icons are ones above the others
. typing area uses only one third of the available space
. I can not click anywhere in the window