Is this Arch Linux specific issue? Does not seem to happen at least on Ubuntu...
I wouldn't say it's an Arch bug per se. Arch is a distribution which always releases new packages so a recent upgrade to gtk2 2.14.4 and glib 2.18.2 broke rainlendar (or some other *bleeding edge* package broke it, I'll let you be the judge of that).
Rainlendar starts ok, but an attempt to open a menu (right click) makes it segfault. I started it with verbose and debug but did not get a trace or a log of any kind.
I had one recuring event set from before and I tried to open a configuration menu for it (by double clicking) and while it was open the right click on rainlendar did not result in a segfault... if that helps in any way.
I tested both b65 and b66.
Together with these bug reports please also see this forum post: