Lately some users (including me) had a problems with uploading files that have .png extension.
According to discussion, in this image: http://e-shuushuu.net/image/513011/
, problem should be fixed. It seems that something messes up again, though.
Unfortunately, I do not observe enough, if other users in past few days had any problems while uploading, but I actually had.http://e-shuushuu.net/image/515510/http://e-shuushuu.net/image/515515/http://e-shuushuu.net/image/517608/
Following Kage's advice, I decided to make this forum topic.
If this is some strange bug's case, I hope this will be fixed soon ;-;