There may be some kind of automatic caps-lock detector that attempts to prevent people from accidentally shouting at one another.
As for the attachment problem, I've seen that before, too. There may just be some kind of error in the attachment handling that is giving a false positive for a damaged file. The last time it happened to me, I just trimmed a few pixels off one edge of the image, and it uploaded fine after that. It was just a screencap for a tutorial, though, so losing a bit of the image didn't hurt anything. You could possibly try adding some transparent padding around your image to see if that clears it.