Problemin kaynağı aşağıdakilerden birisi olabilir:
Taramaya çalıştığınız makinanın firewall'unu geçici olarak kapatıp tekrar tarama işlemini gerçekleştirin. Eğer taranacak makinada firewall'u açtığınızda tarama gerçekleştirebiliyorsanız ve taranacak makina Windows XP SP2/SP3, Vista veya 7 ise, şu linkte yazılanlara bakın question regarding the Windows Firewall setup.
Microsoft dökumanlarına göre:
"WMI , şu işletim sistemlerinde kurulu gelir: indows 7, Windows Vista, Windows Server 2008, Windows Server 2003, Windows XP, Windows Me, ve Windows 2000.
Windows NT Workstation 4.0 SP4 ve üstü: WMI Control Panel içerisindeki "Add/Remove Windows components" bölümünden kurulmalıdır.
Windows 98/95: WMI CORE 1.5 (Windows 95/98/NT 4.0) indirilerek kurulmalıdır. http://www.microsoft.com/downloads
Windows Browser servisi bilgisayar listesini her 12 dakikada bir günceller. Bu esnada bir bilgisayar bilgisayar ağında aktif görünmesine karşın gerçekte kapanmış olabilir. Ancak bu sefer de, eğer ICMP ping opsiyonu açık isei "Ping failed" hatası almanız gerekir. Eğer ağınızda ICMP protokolü (ping, echo) yasaklı ise is not allowed in your network, you might want to disable pinging in Options - Scanner - Use ICMP ping. After this, you will be able to scan online hosts which don't respond to pings, but all offline hosts (and also unoccupied IP addresses) will show the RPC error status, and thus it will slow down the scanning of large IP groups or ranges.
If you scan the computer by name, it could be resolved to an invalid or not existing (unoccupied) IP address due to problems with DNS or WINS. If you scan the computer by IP address, you are likely to receive Ping failed, but if pinging before scanning is disabled, you will receive the RPC error when scanning an offline or unoccupied address (see the previous point). A TNI user has encountered this problem and described it on our forum: http://www.softinventive.com/forum/index.php?showtopic=428
If the scanned name or IP address belongs to a network device which can be pinged, but is not a Windows computer (NIX-computer, network printer, router, managed switch, type library, IP phone, firewall, thin client, etc.), it cannot be scanned via the RPC protocol and shows this error. However, the program tries to scan this host via other protocols (SMB, SSH and SNMP), and the scan result may vary depending on the settings for these protocols and the nature of the scanned network host.