Maybe these users are behind a firewall which prevents them from connecting to the 843 port? For an 'offical' flashpolicyd see: http://www.adobe.com/devnet/flashplayer/articles/socket_policy_files.html

With what you've done, $listA has no element named "Item_One" so that expression is effectively NULL
It's an array, and if you want to get "A" out of $listA, you need to use $listA[0].Item_One and $ListA[0].Item_two
Without knowing more about this situation not quite sure what to suggest...
Do you really have so many items you need a CSV?
If not try a hash table

PS C:\temp> $listA = import-csv .\list.csv
PS C:\temp> $listA

Item_One                                Item_Two
--------                                --------
A                                       1
B                                       2
C                                       3


PS C:\temp> $listA.gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Object[]                                 System.Array


PS C:\temp> $listA.Item_One

PS C:\temp> $listA[0].Item_One
A

PS C:\temp> switch ($Test)
>> {
>> $listA[0].Item_One {write-host $ListA[0].Item_two}
>> default {"Not found"}
>> }
>>
1

# Hash table example
$hash=@{"A"=1;"B"=2;"C"=3}
$hash.A
1

New after Nick's 7/9 comment:

I don't think the case/switch structure is a good fit for this case. This seems like it will do what you need.

$listA | foreach {
    if ($_.item_one -eq "A") {
        # do something
        write-host $_.item_two
    } elseif ($_.item_one -eq "B") {
        # do something different
        write-host $_.item_two
    } else {
        $found = $false
    }
}
if ($found -eq $false) {
    write-host "default"
}

Depending on your needs, the IF clause could also be begin like this

if ($_.item_one -match "A|B|C") {