Here's what the help file has to say about this error:
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If you see a dialog box with the following message after
you start your computer or when you start Microsoft
Windows AntiSpyware, you need to repair or reinstall
Windows AntiSpyware. The following message can also refer
to Error 102 or Error 103:
Warning: Microsoft Windows AntiSpyware has encountered a
critical error (Error 101). Please restart Windows
AntiSpyware and run the program again.
If you continue to experience this problem, please
uninstall the program and install the most recent version
of Windows AntiSpyware. You can use Add or Remove Programs
in Control Panel to uninstall this version of Windows
AntiSpyware.
You can repair Windows AntiSpyware using Add or Remove
Programs in Control Panel. Click Microsoft AntiSpyware and
click Change. Click Next, and then click Update.
If you see the critical error message again, uninstall
Windows AntiSpyware and reinstall it. To do this, use Add
or Remove Programs in the Windows Control Panel. Click
Microsoft AntiSpyware and click Remove. You can reinstall
Microsoft Windows AntiSpyware at
www.microsoft.com/athome/security/spyware/software.
