If I complete a task using Rainlendar (Right Click -> Completed) then the task gets updated as Completed on RTM, but it doesn't get removed from my 'To Do' list in Rainlendar.
I, too, am using the unlicensed b77 version, in my case on Windows 7 RC1 32bit, and have the exact same problem. I'm sorry to repeat the question, but I'm not sure I understood your answer--
Are you saying that this is a known issue, which you will be fixing in an upcoming version? If so, then I will upgrade immediately.
BTW, I totally love this program. LOVE LOVE LOVE it. Have been using the unlicensed version for years. There is nothing that comes close in terms of flexibility and ease of use.