I've got blkUI downloaded and have been using it for awhile, but signed on today and started getting spammed with this error message whenever I enter combat:
Interface\AddOns\WeakAuras\WeakAuras.lua:2335: Usage: UnitIsUnit("unit", "otherUnit")
Time: 10/20/13 14:22:54
Count: 34
Stack: [C]: in function `UnitIsUnit'
Interface\AddOns\WeakAuras\WeakAuras.lua:2335: in function `ScanAuras'
Interface\AddOns\WeakAuras\WeakAuras.lua:1712: in function <Interface\AddOns\WeakAuras\WeakAuras.lua:1709>