SBS2003/ISA2004 SP2 and WSUS Inconsistencies

I'm not quite sure whether WSUS has installed ISA2004 SP2 correctly on
my SBS 2003 server.

WSUS says the ISA 2004 SP2 Approval is "Install" and "REday for
Installation" but the server status says "Not Needed" (but also
"Download Succeeded").

The Application and System event logs both have entries within a few
seconds of each other saying SP2 was "installed correctly" and
"successfully installed", followed by a System Event saying the server
will be restarted within 5 minutes. Then it goes quiet and it seems
that the restart did not happen.

This was a Sunday morning (5 Feb) and remote access/email traffic all
stopped from around that time. On Monday morning, I rebooted the server
and it seems to be working fine since then.

ISA Server Manager now says it is "Version: 4.0.2165.594".

Should I uninstall and re-install the Service Pack?

Tom Walker