Yes, it's sort of like a mystery where you've been handed only a single clue, the implication being there is a dead body lying about somewhere....
My guess is you transferred the "sky.mat" file using an e-mail program that inserted a non-ASCII character at the end-of-line.
Uhm, yeah, this is not a question (nor is it a very good post title). It sure looks like an error message from the Radiance executable
oconv
, but without more context or even a working link to that image, we cannot really help.