Not much that you can do than wait (or build the image by yourself).
libubox was updated yesterday and the new version is contained in the firmware images (created by the phase1 buildbot for ath79), but other optional packages (like luci) are compiled separately by the phase2 buildbot (for mips_24kc), and there the new build run is not yet completed, so the known packages list differs from the phase1 results. (depedency list claims an older version of libubox than the one that you already have in the image itself)
You have had bad luck in timing, as there have been recent commits breaking the compatibility to the situation week ago.
You need to reinstall new firmware and packages.
(and like lleachii says, it is best to install additional packages quickly after installing the firmware, so that everything are compatible)
Thanks all,
One additional question.
I have the Netgear WNDR3700 v5.
In the list there is a column for install URL, Upgrade URL, Snapshot install URL and Snapshot upgrade URL.
I have loaded openwrt-ramips-mt7621-netgear_wndr3700-v5-squashfs-factory.bin to install openwrt.
Do I now need to use openwrt-ramips-mt7621-netgear_wndr3700-v5-squashfs-sysupgrade.bin for the upgrade?