https://bugs.freedesktop.org/show_bug.cgi?id=50135
--- Comment #8 from Micael Dias kam1kaz3@gmail.com 2012-09-10 12:44:16 UTC --- Created attachment 66925 --> https://bugs.freedesktop.org/attachment.cgi?id=66925 OgreSampleBrowser - Shadows
Appears to be related.
I'd say it looks like a depth precision/bias issue, but I'm not sure.