Problem With D String at 5th Fret

[binge]

So I have a Vigier Excalibur Supra and I use Ernie Ball 9s.  When I play the A note at the D string on the 5th fret the note first sounds, then quickly turns into a harmonic then loses it's sustain very quickly.  Anyone know why this is happening?  It happens nowhere else on the neck and the other strings at the 5th fret are all fine.  

[Ben]

Hi Binge,            Do you use 9-42 or 9-46? If you have swapped to 9-42 you may need to look at the set-up / action / intonation etc.

[binge]

hi Ben, Thanks for replying.  The strings I use are 9-42.  I guess I need to put on the Ernie Ball Hybrid Slinky and see if that helps.Many thanks!