Buzzing sound...Truss Rod?

[ii7-V7]

I got a new fretless SX bass for X-mas. All in all I was suprised by the quality. Two things that weren't perfect were the truss rod, which would hardly budge, and a strange buzzing sound on the Bb adn Eb of the A and D strings (first "fret"). When I say strange buzzing sound I mean that it isn't quite the same as the normal buzzing you here when the string are to low, or there is a high spot on the board.

So, since I wanted to replace the nut and finish the board anyway....I went ahead and did that. After sanding and flattening the board, installing a new nut, shimming the neck pocket, installing new strings, and setting the bass up it plays and sounds beautiful. But the buzzing under the Bb and Eb (first "fret") is not only still there it actually sounds worse.

The only thing that I can figure is that its the truss rod vibrating under those two notes. I can't think of anything else, except maybe that the fingerboard is cracked.

So, what to do?

[Figjam]

That sounds suspicious. The fact that you replaced the nut and it is still there makes me tihnk you may be correct, the truss rod may be loose or somethnig of that sort.

[Snarf]

Probably came unglued. My Carvin did that. Not a cool sound.

[ii7-V7]

Any way to fix it? I really don't want to have to take the fingerboard off!

Chad