I'm using ZD v 2.0 beta 4 (zdesktop_2_0_beta4_b10514_macos_intel on Mac OSX 10.5.8).
If I click on a particular message in the list pane, as expected the text of the message appears in the reading pane. However, if I then click on the Inbox folder in the left-hand Accounts pane, it causes a checkmark to appear in the checkbox next to the previously highlighted message.
This is a change in behavior from what happens via the web browser interface. Normally, clicking the Inbox will clear the reading pane of the current message text and remove the highlighting on the last selected message. Is this the desired action? It makes ZD behavior inconsistent with the web interface.