Strange fret buzz?

[stillborn86]

Ok. I'm new here and I don't even know if this is the right forum for this post, but I have never even heard of this before.

The other day, I was playing Metallica's Orion and I started to get a bit of fret buzz. There's a point where the tablature goes from:
|----------------|
|----------------|
|5-----5-----5-5-|
|--7-7---7-7-----|

to:
|----------------|
|----------------|
|6-----6-----6-6-|
|--7-7---7-7-----|

I usually just hold the 5 and 6 on the A string until I have to let go of the six. The buzz is coming from the first part, and I contributed it to the fret bending the string since I hold the string down in both the 5th and 6th position until I have to let go of the 6.

So I changed the strings and the buzz is not gone. I keep playing around trying to find the problem, and only find more questions...

The buzz only happens when I have the D and B (5 and 7) pressed at the same time. If I release one or the other, the buzz goes away. I guess, technically I could just play them one at a time, but that doesn't fix my problem.