Point defects in slab structure - resonant frequencies

I am trying to look at the band structure for a slab PC structure.  
I used a non-defect structure to identify the bandgap for guided 
bands and then introduced a point defect in the center of the 
structure to introduce localized states in the gap.  I have tried 
a few different supercell sizes and grid resolutions, but I have 
not yet "clearly" seen localized bands in the gap region.  

Please see the following image of my band structure, for a 
5x5x5 supercell, 10x10x10 resolution, and 85 bands plotted. 
http://img530.imageshack.us/img530/1847/slabdefect555supercellyf1.jpg

I feel I can see one band that is approximately flat around 
normalized frequency 0.28, but then there are some other 
bands in there, as well.  Is my problem due to a too-small 
supercell or should these other bands actually be in the gap as well?

Why am I trying to use MPB rather than MEEP to find 
resonant band frequencies? I am new to both of these 
software packages and cannot understand yet how to
simulate non-rectangular unit cells in MEEP (despite
your posts on this on theMEEP list).  But that is 
a discussion for a different list.  
Thank you,
Rob