I just installed the gallery and am having this same problem in 1.7.11. When I try to upload I get the "CSRF check failed" and, thought I've searched the forum and tried whatever suggestions I've found, I can't get this to work. I really like the gallery but I can upload video files and only some image files.
Please, I know this has been an ongoing solution but if anyone actually has figured out the problem, and can possibly post a fix in english, that would be great.
stu