Hi Vitaly, welcome to the forum!

Yes there was a change to the right-click behavior to only be a shortcut for "Done" and not "Cancel", it was discussed previously here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=8966.13

But you can switch it back to v3 behavior by an option in moi.ini . Go to Options > "Edit .ini file", and find this setting:

[View]
<...>
DoRightClickCancel=n


Set it to say =y instead and you should get the old right-click canceling behavior back.

- Michael