VPI SDS producing hum at 45rpm

Noticed that my SDS is producing a hum when the needle is in the groove, but only when running the SDS at 45 rpm. If I lift the needle up, the hum stops. If I leave the SDS at 33rpm and change the belt to the 45rpm position, I can play LPs without a hum.

I just switched from a Dynavector 20SL to a Dynavector XV-1s today. My SDS is adjacent to my turntable. If the proximity were to be responsible, wouldn't I hear it all the time - not just when the needle comes in contact with the LP?

Thanks in advance for any advice.
Contact VPI, they are very helpful.
I've never had any luck getting ahold of them, actually. Their phone system doesn't allow for messages and they've never picked up the times I've tried.

This morning I'm noticing the hum at 33 rpm too. I wonder if the exposed design of the XV-1s is more susceptible to interference from the VPS. I can't easily move my VPS so I'd like to get a good feeling that that is the problem before I go through the hassle.
I assume you've already tried the TT without the SDS connected and the hum went away, if that is the case see if relocating the SDS helps, if not email VPI.

I did have a hum problem even without the SDS, but it was a different problem (and the solution was crazy), but I have more info on the SDS.

If I run the SDS at 33 and change the belt to 45, it runs fine. With the belt at 33 and using the SDS at 45 rpm, I can hear the same frequency of the hum emanating from the TT (arm still on arm rest). When I touch the arm (e.g. to move it) it is vibrating. Not visibly but it feels like you're holding an electric razor. Also, when starting up the TT at the 45 setting on the VPS, the table shakes violently (on top of my Cloud 9).
So my problem was that my table, while nicely isolated from the shelf (via my Cloud 9), wasn't perfectly isolated from the motor. A simple shift solved the issue.
the exact same thing happened to me! same solution too!
Happy Holidays!