Here's whatsnew:

"the link to neoraine win32 binary was broken and I forgot libefence in the linux build.
...
After checking, it was the wrong binary, it was still 0.50.11 (you could see it from the date of the binary !).
...
I upgraded the download page with the correct 0.50.12 (renamed 0.50.12b because of the stupid cache proxy on this site)".

Get it here:
http://www.rainemu.com/html/download/latest.html

-Trebor