Problem with bwlabel function

Hi all, may I know if there's any limitations to bwlabel function? Last time, i was able to use bwlabel to label the pit areas for my binary image which gave me exactly what I need.

However, now that I am using another image, it just couldn't label the areas at all if i use 8 as connectivity. When I used connectivity 4, it didn't give an accurate result. Does anyone know why?

[Anand]

Please upload the image.