A common problem people notice when building reports with the simple report builder using the asset type of "Computer" is that virtual machines do not show up in the results of the report.
Some Background Info
Inventory Solution 6.1 SP1 introduced the Virtual Machine classification of machines. This means that any virtual machine that was previously displayed as a "Computer" will instead show as the new "Virtual Machine" classification of device.
When a user creates a new report using the simple report builder and clicks the finish button, the following piece of SQL code is appended to the query generated:
where/and [ResourceTypeGuid] = '493435f7-3b17-4c4c-b07f-c23e7ab7781f'
The "where" exists if no other criteria have been defined otherwise "and" will be in its place.
The problem with this code is that the resource type GUID "493435f7-3b17-4c4c-b07f-c23e7ab7781f" is the GUID for "Computer" and is therefore filtering out all other computers.