It looks like a bug in .Net Framework. I've made some changes to the image and added logging messages. So lets check it again when beta #6 is released.
I've only checked it a couple of times (straight after opening b4r and it happened each time. I've only ever opened 'About' in b4a a few times and never seen the above. Looks like @inakigarm has sorted the logs for you so I won't duplicate (unless you want a second set).
I'll help out with testing were I can but other's will probably beat me to it anyways