EDIT EDIT EDIT:
Sorry for the wrong information I supplied, I was misled by the background of the emulator I’m using, saying “Amiga emulator by Chui” and displaying a “Dreamcast Amiga uae4all” logo. Since, as I said, I couldn’t remember exactly where I got hold of the emulator I had just googled Chui’s emulator (whose page looked familiar) and posted the link to it.
The emulator I’m using is exactly the same one user “asiainorama” linked to above. As far as I understand it’s a modded version of Chui’s Dreamcast emulator for the RPi.
Get this one!
I had encountered the same bug upon installing RetroPie 1.8.1.
With no Linux knowledge whatsoever I spent a lot of time searching for a solution on the net – I don’t know where I came across my final solution (possibly I did on here), but this has been working on my Pie for quite some time now:
Chui’s Dreamcast emulator (http://chui.dcemu.co.uk/uae4all.html).
Some random games don’t seem to work, but I’d say at least 95% of my collection run without any problems.
Also, there wasn’t any trouble configuring anything, mouse and two-player joystick support were available straight away.