I am sure that this version is not free of bugs because it is the 0.2-Alpha version.
But i've a better experience with this version then the current stable version 0.1.1-stable.
Especially, creating messages within html is much better then within 0.2-Alpha.
When i switch to html, I can see the inbox and all the boxes in it. No problems here.
Maybe you must send a first e-mail to the user. to see the folders...
You can also have a look in the RoundCube logs directory.
As you can see here
the 0.2-Beta version is not far away!