Try checking the error values to see if it is failing or not. Since it's an object I dont think it would display anything if you tried to view $adsdomain or $adsgroup. You can view properties of the object however like...

$null=messagebox($adsGroup.name,"",0)

Code:

$adsGroup = GetObject("LDAP://cn=$Group,cn=$GroupOU,dc=$DomainName,dc=$Toplevel")

If @Error <> 0

   $null = messagebox(@SError,@Error,0)

Endif