mysql_num_rows HELP

Hi

Sorry for my terreble english.

On my local (win) comp i have apache+mysql+php 4.05
I'm counting rows using mysql_num_rows function, and everything works fine.
When i upload php file on server it says:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result
resource in /home/optikara/public_html/crosun/izn/insert_form.php on line 80
Server runs php 5.0.5

Code is:
--------------------------
//connect to database code goes here

$result_v_smjestaj = mysql_query("select * from v_smjestaja order by
v_smjestaja_naziv ASC", $db);
// some other html code goes here

if (mysql_num_rows($result_v_smjestaj)) {
print "\n";
while ($qry = mysql_fetch_array($result_v_smjestaj)) {
print " value=\"$qry[id_smjestaja]\">$qry[v_smjestaja_naziv]";
}
print "\n";
}
--------------------------

On my local comp this works. Plz any solution, in plain simple code:)))
tnx in advance.
Dejan