Would a jump in refresh rates in your level indicate a bad block somewhere?

I have an area in my level where my fps drops from 50fps to about 37 fps. Debug shows an increase in time for refresh - see the screen shots below. You can tell from the image I have only moved the camera slightly between the two screen captures and most other statistics have stayed the same (number of polygons etc).

Would this indicate a bad block?...because I have been backing out many changes and messing around - but can not figure out what is causing the drop. Please help. Any direction for debugging this appreciated.