This problem has been reported in the following java.net forum:
http://forums.java.net/jive/thread.jspa?threadID=58771&tstart=0

"With Windows Defender SpyNet on Vista set to Advanced and installing Java Update 14 b03 a Windows Defender warning appears that the publisher could not be verified for the IE plugin. Suggest digitally signing the DLL to prevent such warnings. Note that by default Defender is set to normal so that majority of users will not see this warning."

See attachment for a screenshot.