If you are diagnosing an inventory issue, and want to know what information the client is sending to the NS; and what is occurring on the client during the inventory collection process; then here are some suggestions on how to get more information.

These steps use the diagnostic tasks from the following KB article:
For an example Altiris client tasks see:
   How to adjust Altiris Agent logging
   http://www.symantec.com/docs/HOWTO75097
 

Prepare clients to collect additional detailed information

1. Confirm that the client of interest is able to receive and process tasks, by using the task: Agent: Return IP Configuration, from the above tool kit.
If they are not able to run tasks, then you may need to use policies, instead of tasks.

2. Configure the client of interest to capture NSEs (NS events) as they are sent to the NS, by using the task: Agent NSE Capture: Enable.

Note: After testing, be sure to disable NSE capturing.

3. Optionally, to confirm that NSE are being captured as expected, have the client of interest send basic inventory to the NS, using the task: Agent: Send Basic Inventory; and then see that a new NSE file was captured on the client.
 

Create and run a new task to collect inventory data

4. Create a new Gather Inventory task, such that:

Collect the one type of inventory data of interest (hardware and operating system, software, file properties, server applications).
Limit the data classes collected on hardware and operating system or server applications to include data classes that appear to have an issue, as well as one or two data classes that are known to be working properly.
On Advanced Options, on the Run Options tab:

Uncheck "Send inventory changes (deltas) only"
Check "Enable verbose client logging"

For additional information see:
   Inventory Solution 7.0 SP2 Introduction and Troubleshooting Guide
   http://www.symantec.com/docs/HOWTO21693

Note, temporarily disabling the regularly scheduled inventory policies, can help ensure that they do not interfere the current testing.

5. Run the above Gather Inventory task on the client of interest.

6. Monitor the task on the client to confirm that it has completed as expected.
 

Collect client-side Results

The most relevant files are:

1) The captured NSE files

These files contain the information that the client sent to the Notification Server (NS).
By default, the task described above configures the client to store these files in c:\NSEs\

2) The Altiris Agent logs

These files contain additional information about the process of collecting information.
In Windows XP, by default, they are in c:\Program Files\Altiris\Altiris Agent\Logs
In new versions, by default they are in c:\Users\Public\Public Documents\Altiris\Altiris Agent\Logs\
typically the files are named agent.log, agent1.log, etc.
 

Review Server-side Results

Confirm that basic inventory information has been received for the client of interest:

In the Altiris console:
Locate one of the computers of interest
View the computer using the Resource Manager
View a Basic Inventory data class (such as AeX AC TCPIP)

Menu: View > Inventory
Center column: Data Classes > Inventory > Basic Inventory > AeX AC TCPIP
Right column: on the Status (tab), In the General (section)

Check the date: Data Last Received, and confirm that the data is reaching the NS as expected.

Confirm that the data classes of interest are received as expected. Use the steps in previous step.
 

Review Client-side results

Review the captured NSE files, to see what information the client sent to the server. These files can be viewed using a text editor. An editor with XML capabilities is preferable. Note: the data class GUID is shown in the Resource Manager on the Status tab in the Database information section.

Review the Altiris Agent logs, to see what occurred while the inventory was collected, and specifically whether the Altiris agent collected the expected data classes,
and whether it had any trouble collecting that information.

There are several utilities for viewing agent logs, one of them is
   Symantec SSE Tools for ITMS
   http://www.symantec.com/docs/HOWTO60787
 

Hardware Inventory specific comments

Note, the following comments are specific to hardware inventory collection.

1. After the inventory gathering has run, review the Altiris Agent logs.

You may find an error similar to the following.

Error while performing simple query <server=\\.\root\cimv2> <query=select SerialNumber from Win32_BIOS> <value=SerialNumber>: Access denied. (-2147024891)

2. If you suspect that the Inventory gathering process had trouble collecting data from WMI, then see what the WMIC command-line utility report. See:

WMI Tools and Utilities (WMIC, WEBMtest)
http://www.symantec.com/docs/HOWTO26064

And for a Microsoft KB:
Windows Management Instrumentation Tester overview
http://technet.microsoft.com/en-us/library/cc759703(v=ws.10).aspx

In this example you can run the following command to see all values in the WMI class

wmic path Win32_BIOS get * /value

Or you can use the following command to see a specific

wmic path Win32_BIOS get SerialNumber /value

If you can access the managed computer via an RDP connection then you can run these and other commands directly.

However if you do not have easy RDP access, or if running the commands while logged on is successful but the inventory gathering still fails then you may want to try run these commands using Altiris tasks. For details about using tasks in this manner see:
About using Altiris client tasks in diagnosing client-side issues
http://www.symantec.com/docs/HOWTO75155

3. You may find that for the requested item:

WMI may return a Microsoft Windows error. If so, the following KB article may be helpful
   WMI Isn't Working!
   http://technet.microsoft.com/en-us/library/ff406382.aspx

WMI refuses to return the information, due to permission issues, If so, the following KB article may be helpful:
   Authorize WMI users and set permissions (Win 7, WS08r2)
   http://technet.microsoft.com/en-us/library/cc771551.aspx

WMI returns an empty value
   This might be correct, such as if there is no BIOS serial number.
   Check to confirm that this is the correct value, and
   If so, ensure that this empty value was written to the NSE

WMI returns a non-empty value
   Check to confirm that this is the correct value, and
   If so, ensure that this empty value was written to the NSE

Possible Next Actions:

If the the Inventory gather process had trouble collecting certain information, then focus on addressing issues that prevent the inventory data from being collected.

Otherwise, review the NSE file to see if the expected data was written into these files.

And if so, then check the NS database to see if the data is now being stored as expected.