Kyle asked "Is it common to have brood appear above a queen excluder?  What could have
caused it? "

Yep...it is reasonably common.  In my experience, perhaps 1 in 20.   

There are at least a few possible causes:
1.  A wire is bent and the queen can get up (and back down).   
2.  A new mated queen entered the box above the excluder.
3.  A queen was accidentally moved above the excluder by the beekeeper.

Don't let anyone tell you that WORKERS MOVED EGGS UP.  I was once at a conference where several researchers and queen breeders were present.  This old wives tale (workers moving eggs) came up.  The moderator asked for a show of hands who had experienced workers moving eggs...NOT A SINGLE HAND WAS RAISED.

When this happens to me, I look for the queen in the upper box.  If I can't find her, I assume that the excluder has a bent wire (something that can be very hard to see) and discard it.  Don't try to straighten it; it can be a frustrating job and rarely works.  

Lloyd
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http://www.rossrounds.com
Lloyd Spear, Owner of Ross Rounds, Inc.
Manufacturer of round comb honey equipment and Sundance pollen traps