I use RD Tabs since a few weeks now and love it. All i noticed in minor issues is that the thumbnail view is not working well. It does open all the screens, but has trouble updating them in thumbnail mode.

Now this is not a horrid problem, but it is one of those much enjoyed features

Yes, this is a known bug. There is a problem capturing the thumbnails due to some network optimizations introduced in the latest version. It's actually something I can't workaround (I can't capture the thumbnail whent he screen is black according to the RDP control). As such, I'm going to allow this network setting be optional. It has other drawbacks I've found elsewhere. Such as if you are on a slow connection, a full screen refresh is required when you switch tabs, which is not optimal. What you gain with this optimization is that when a tab is not active, there is no network activity as the tab is effectively "paused."