My roommate is having this issue and were both really sick of it.
After she gets about 3-5 pull ins from fishing it starts to give her the "You didn't catch anything " message for the rest of the time, this goes on for quite a bit, she did it 20 times in a row and continually got the message, she hasn't hit the 200 limit nor is her character new, this has been happening for the past year now and its starting to annoy her, we did the file scan to see if there was a bad sector but nothing was wrong, she has tried this on different systems(ps2,ps3,360 and pc).
Now she stops fishing for sometime and then trys to start up again and the same thing happens, It also doesn't matter were it is any zone any place anytime,Also her character is over lvl 20 so the fishing fatigue thing is not a factor. On my end everything is fine so either its her character all together or something in the .dat files that is cutting out causing this.
If anyone has any idea or has had the same thing please file us in on what you did to fix this issue
Thank You