[R-sig-Geo] problem with 'islands' in neighbourhood matrix

[Meredith Franklin]

I created a neighbourhood matrix in GeoDa and have read it into R using 
read.gal (spdep package).  I have a few zero-neighbour polygons and as a 
result I cannot apply nb2listw to my nb object.  Is there a way to get 
around this problem when reading in the .gal file or do these islands 
need to be removed before creating the matrix?
Thanks,
Meredith Franklin