Reports "Count OS versions" and "Count OS and Service Packs" incor

The Reports "Count OS versions" and "Count OS and Service Packs" are not only
redundant, they're incorrect. I have 77 machines showing up in the console
with client installed (and others that don't have the client yet). If I run
the report "Count Processor type", the number of machines is correct at 77
total. However, when I run either of the OS reports, the count of machines is
incorrect, being very light on the Vista machines in my domain (4 listed,
about 40 in the console). The numbers on the XP nad server machines listed
appear to be accurate. This seems to be affecting the Vista machines in
partcular.

Has anyone else run into this, and is there a known fix?