This is Credens Justitiam or Mami's Theme song from Mahou Shoujo Madoka Magica (Puella Magi Madoka Magica).

It is sung by Yuki Kajiura and the language is Kajiuran. It's a made up language that Yuki Kajiura uses for her own personal use in a lot of her songs that apparently no one else in the world can understand. It's a mix of Japanese, Latin, and other European languages.
Since this is a fake language there are a few different versions of the lyrics, these where the ones I thought fit the best

DOWNLOAD:
http://www.mediafire.com/?23ar1hn3mun...

The Lyrics:
Salti roiyary tamarie pastiarasa resting (ah~)
Salti roiyary pirarya soltia reiya resting (ah~)
(Huwa) Gritariya pirarifu safariha
(yui) Yasoriiya (il) zay fariya (Salti roiya)
Salti Oane
Salti roiyary tamarie pastiarasa resting (ah~)
Salti roiyary pirarya soltia reiya resting (ah~)
(Huwa) Gritariya pirarifu safariha
(yui) Yasoriiya (il) zay fariya (Salti roiya)
Salti Oane
(Huwa) Gritariya pirarifu safariha
Yasoriiya zeei fariya (Salti roiya)
Salti Oane (Ah~)
Gritariya pirarifu safariha
Gritariya pirarifu safariha
(Huwa) Gritariya pirarifu safariha
(yui) Yasoriiya (il) zay fariya (Salti roiya)
Salti Oane (Ah~)
Salti roiyary (Ah~) tamarie patiaraiya riiya