This is usually caused by WebSence or Surf Control (and their likes) or problems with the proxy.
Find what is being blocked in WebSence or Surf Control and make sure that the sites in the patch log are accessible to download updates.
If that still fails, double check proxy settings or allow the core access without using the proxy.
LANDesk EMEA Technical Lead
I had a similar problem downloading definition updates using LDMS8.7 SP5. I had *.landesk.com added to the ACL of our Proxy and now it is working fine. Hope this helps.
I also have seen the same error with Websense filtering. Even putting it in the allowed list would not fix it, I had to bypass the IP address all together.
I have also seen this with Surf Control - The only way that i found to get around the error is to Bypass the proxy server.
FYI - i have also seen that it have a problem with ISA server - so you may need to add an exception to your ISA Server if you have one.