SKB PS45 pedalboard and JVM issue

Squeal/feedback issue.

Got a SKB PS-45 pedal board (same as Furman SPB-, set it up with Marshall JVM 205c. The board has a patch bay. I set it up to have my tuner and distortion pedal through the front of the amp, the delay and sonic stomp are through the effects loop. Remember, all this is going through the patch bay of the pedalboard.

Everything works great through the clean channels (green, orange and red). BUT the problem is when I click on the overdrive channels of the JVM, it produces a piercing, feedback like squeal. And yes, this is with the distortion pedal deactivated.

Here's how it's hooked up. Look here, Example #5 in this manual, page 6:
http://www.furmansound.com/pdf/manuals/SPB-8_manual.pdf
Only difference is that example five shows a "remote mono effects" unit whereas I'm using pedals there instead (same purpose).

What do you think? Is there a simple fix? This is my first experience with a powered board and patch bay, I need your expert advice.

Fixed it.  Two things it could have been, I didn't bother to trouble shoot each one to find out though, since it works now I don't care.

1.  If running a powered board, make sure all batteries are out of the pedals.

2.  Some pedals don't play nice with one another. 

It was one of those two that caused the issue.  Hope this helps someone in the future.

They're an odd thing, pedals....

I ran two pedal boards straight into the front of my old 100W valve combo for years and years with no issues other than the the hiss that comes with running all that extraneous stuff, even with a noise gate on the end of the chain.
The order that everything is chained together is very important and I forget now what the optimum order is.... Quality cables are a must!!