[CentOS] Find and excluding directory

Hi

I have to use find to change the perms of a directory and files within 
that directory recursively but i need to exclude a directory within the 
top level directory, as its a netapp and so contains a read only 
.snapshot dir.

I have tried...

# find /var/data/foo -path '\.\/\.snapshot' -prune -o -exec chown 
usera:groupb {} \;

but

chown: changing ownership of `/var/data/foo/.snapshot': Read-only file 
system
chown: changing ownership of `/var/data/foo/.snapshot/hourly.0': 
Read-only file system
chown: changing ownership of 
`/var/data/foo/.snapshot/hourly.0/filename': Read-only file system

any clue ?

thanks