I think I hit a rare bug. Using b53, default skin (Shadow4), with "Transparency Type" set to "Region", the Calendar will show partial overlaps when I switch to another month. (see attached screenshot below.)
I'm using Vista Business 32, btw.
I never noticed it before, but I did some tests just now and found the exact problem started with b49. B48 is alright, so is b44.
No problem with the other skin (Chromophore), and no problem if I switch the Transparency Type to Copy or Native. (Native doesn't work for me, however, since I want the Rainlendar windows to stay on my desktop.)
Anything else I should try?