D string refuses to intonate

[illumina]

Heya,

newbie here.

I have a 6 string guitar tuned 1/2 down with Ernie Ball 10's. The problem is : with the D string is correctly in tune at the 0th fret, but almost a whole semitone off on the 12th! I moved the saddle all the way up, and this hasnt helped.

I recently got the body back from a paint job, ad assembled it. Everything is perfect, except this string. Do I have faulty string? Every other string is perfectly in tune and intonates fine.

Thanks for your help,
~eric