I have a similar issue.
I can upload large files (over 100MB) just fine.

I now have one that is 130MB and it starts loading and gets about 7 percent done and then the black box pops up stating error uploading file.

I have gone back after this and uploaded other large files with no problems. My settings should allow files up to 200MB to be uploaded. Any suggestions?

(I am new - just installed dolphin 3 days ago, so i do have the newest version with ads for now).