Scott - thank you for sending this our way.

First off, I want to be sure you're running the latest version of MBSA 2.1
(version 2.1.2104) since there are lingering issues with MBSA 2.0.1 and the
original release of MBSA 2.1 (version 2.1.2102) that could cause this
problem.

If you're already using the latest version of MBSA 2.1, you may have a
corrupt Windows Update Agent on your target machine.  To correct this, go to
the target machine and follow the steps listed in KB 910336
(http://support.microsoft.com/kb/910336).  The error codes in this article
are not the one you're seeing, but the resolution (to remove the
SoftwareDistribution folder and allow it to rebuild itself) is likely the
best fix.  In an extreme case where this does not solve the problem, you can
re-register the Windows Update Agent DLLs and re-initialize the WUA client
which effectively refreshes it to its initial (and best possible) state.
You can do this by following the steps below:

Start --> Run

CMD

Click OK.

Enter these in Command Prompt Window ONE at a time, pressing ENTER after
entering each one:
(Patience on the first and last ones especially..)

net stop wuauserv
regsvr32.exe wuapi.dll
regsvr32.exe wups.dll
regsvr32.exe wuaueng.dll
regsvr32.exe wucltui.dll
regsvr32.exe MSXML3.dll
net start wuauserv

Close the CMD Prompt Window.

Open Internet Explorer and manually go to this page:
http://update.microsoft.com/microsoftupdate/v6/

Please let me know if this solves your issue.