Problem running 'top' when ldap is around

[Stephen Allen]

I've noticed that with "files ldap" in nsswitch.conf, if I try to run 
"top" and the ldap server is not available, it takes about a minute to 
start showing information, whereas normally it's instantaneous.

The problem seems to be the mapping of uid numbers to usernames (the -u 
options prevents this).  The man page says:

"Normally, top will read as much of the file "/etc/passwd" as is 
necessary to  map  all the user id numbers it encounters into login names"

So my question is, top must be finding a uid number that it can't match 
in /etc/passwd, then going on to search ldap.  How can this be?

Thanks,
Steve :)