Hello Richard,
Have a look at this post. It may be relevant to your problem.
Subject: Windows Defender error message
2/27/2006 6:14 AM PST
By: ffjuser
In: microsoft.private.security.spyware.general
If you are using the Web Interface to view this forum.
Type your error code 0x80004003 into the Search box and choose either
the Announcements group, the General Discussion group or any group.
I hope this post is helpful.
Let us know how it works ºut.
Еиçеl