[Big Tom]

I had some problems with the installation - actually the load of the database (very likely cause by timeouts because of server load at my webhoster). Re-running the installation script did not work because the tables were already there. My suggestions:
Insert this right after the
// SQL queries array
$query = array();
lines

$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}admlog ";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}favorites";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}laston";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}categories";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}comments";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}products";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}settings";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}sort";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}admingroups";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}notify";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}users";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}ipcache";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}iponline";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}adtypes";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}feedback";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}stats";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}payments";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}bidding";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}bids";
$query[] = "DROP TABLE IF EXISTS zipData";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}cache";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}extrafields";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}productextras";
$query[] = "DROP TABLE IF EXISTS {$pp_db_prefix}currency";

Second suggestion:

Add a line

print "<b>1 - Line: ".$iquery."</b><br />";

right after this in the upgrade/install file
for ( $x=0; $x < count($query); $x++) {
$iquery = $query[$x];
$iquery = str_replace( ";", "", $iquery );

That avoids timeouts and shows that something is still going on....

Last but not least: Add the prefix to to zipcode table...

Tom