siunitx error: "package expl3 too old"

Dear group members,

After updating MiKTeX 2.9 recently, when trying to use the siunitx 
package, I get the following error:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
! siunitx error: "support-outdated"
!
! Support package expl3 too old.
!
! See the siunitx documentation for further information.
!
! For immediate help type H <return>.
!...............................................

Updating MiKTeX doesn't help (it is in fact what caused the error).

What is the simplest way to fix this?  I assume I either need to 
downgrade siunitx somehow or update expl3.  The package will surely be 
updated sooner or later in MiKTeX, right now I am just looking for the 
least-effort immediate solution ... (I don't have much experience with 
manual package installation.)

Thank you for any suggestion in advance.


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