media9: "l3kernel too old" (support outdated)

I recently had this issue with media9 and beamer.

When I tried updating the packages didn't work for me. What worked however, was to remove and reinstall them (l3kernel and l3packages) using miktex package manager.

Just to add to Chris's answer above: You may need to run the MikTex Update Manager in both Admin and non-Admin modes. In Windows that means:

Start -> All programs -> MikTex 2.9 -> Maintenance -> Update

and

Start -> All programs -> MikTex 2.9 -> Maintenance (Admin) -> Update (Admin)