I had this problem on 50% of our PC's here and the fix was one or both of the below:
1. Checkpoint Secure Remote client software. Uninstall this software and push your scan, than you can re-install.
2. run "netsh firewall set service type = remoteadmin mode = enable" (no quotes) in command window.
All clients are of the XP OS... SP2, SP3, x64, etc...
Hope this helps people out there as this seems to be a fairly widespread issue.
Regards,
John Keating
Tachi-S Engineering USA.