Take a look at Manage -- Filters -- Computer Filters

There is a filter there called "Blacklisted Host Computers".  In our environment this filter is blank.  Take a look at yours and see if there is another filter included or if resources are included here.

I am getting blacklisted errors as well. I checked the blacklisting filters and they are empty 

Failed to refresh Policies. The Policy Manager returned error:

The specified host resource has been blacklisted

Examine log for details.

I'm seeing the same thing from one PC in particular.

Log File Name: C:\Program Files\Altiris\Notification Server\Logs\a.log
Priority: 2
Date: 3/30/2010 11:15:31 AM
Tick Count: 1138633265
Host Name: OMHQ54D7
Process: AeXSvc (9452)
Thread ID: 4
Module: AeXSVC.exe
Source: Altiris.NS.ResourceManagement.MessagingResource.Save_Impl
Description: Attempt to save messaging resource with guid OSS-063501 (6f25f8f7-b8e6-4298-82e0-16124a1286b2) has been blocked by the Host Resource Blacklist.

I have both "Blacklisted Host Computers" and "User COnfiguration Blacklisted Users and Computers" filters.  Neither contains any members, and on top of that, neither has any definition (i.e. no query, no explicit inclusions, nor exclusions -- nothing).

When I search for this computer in the "search" box, I find a Computer Resource that was updated at recently as a few minutes ago (and is over a year old).  The asset's status is Active.

With that in mind, I don't know where else to look for this device, and how it might be blacklisted.

All,
I have flagged this thread for Symantec Support investigation.  Can everyone confirm the specific version of SMP they are running (i.e. 7.0 SP2, SP4)?

Kyle --

We're running the following:
Client Management Suite 7.0.9
Symantec Management Platform SP2 HF2 (7.0.5243)

Single notification server (no hierarchy).

I have looked at a number of things including the item browser and see that a good number of previous V6 policies still are present.  I have confirmed that the migration from 6 to 7 in terms of agent upgrade is not advised due to a number of residule V6 Client pieces being left behind.  Symantec now recommends that a full uninstall of the V6 client be removed from the envirionment before running the migration wizard.  Perhaps this is related to the issue of Blacklisted Computers, though I don't recall seeing the errors until recently.  Perhaps removing the agent from the machine(s) that have shown the error and re-installing will be the solution...Just a thought.

A KB article was published yesterday regarding this issue, though the resolution provided is the same as what was mentioned above (i.e. removing the clients from the Blacklisted Host Computers" filter.  FWIW, take a look at AKB52048.