When viewing a newsgroup in Outlook Express 5, some or all of the newsgroups
to which you have previously subscribed may show no headers, but just the
field "Message List Control."

This could indicate that either your system clock date is incorrect, OR:

One or more of the DBX files associated with newsgroups has become
corrupted. Close Outlook Express , then, in the directory holding your
message store (click Tools/Option/Maintenance and Message Store button to
find), rename the associated *.DBX file to *.OLD. Then re-open Outlook
Express 5, and when trying to view the newsgroup, all information will be
updated from the server.

NOTE: All information about whether messages are read or unread will be
lost.

Others have reported that doing a Compact of All Folders has resolved the
problem.  You might also want to check that the option to Compact Files in
the Background is *NOT* checked. (Tools/Options/Maintenance)