i'd say it is not cron, but the flash updater itself...
my output is as follows. note the 404 error, it seems to be the source of the problem
update-flashplugin-nonfree -iv
options : -i -v --
temporary directory: /tmp/flashplugin-nonfree.xS5MKphHxB
importing public key ...
selected action = --install
installed version = 11.2.202.335
upstream version = 11.2.202.336
wgetoptions= -nd -P . -v --progress=dot:default
downloading http://people.debian.org/~bartm/flashplugin-nonfree/fp.11.2.202.336.sha512.amd64.pgp.asc ...
--2014-02-05 16:17:18-- http://people.debian.org/~bartm/flashplugin-nonfree/fp.11.2.202.336.sha512.amd64.pgp.asc
Auflösen des Hostnamen »people.debian.org (people.debian.org)«... 206.12.19.5, 2607:f8f0:610:4000:214:38ff:feee:b65a
Verbindungsaufbau zu people.debian.org (people.debian.org)|206.12.19.5|:80... verbunden.
HTTP-Anforderung gesendet, warte auf Antwort... 404 Not Found
2014-02-05 16:17:18 FEHLER 404: Not Found.
wget failed to download http://people.debian.org/~bartm/flashplugin-nonfree/fp.11.2.202.336.sha512.amd64.pgp.asc
downloading http://people.debian.org/~bartm/flashplugin-nonfree/fp10.sha512.amd64.pgp.asc ...
--2014-02-05 16:17:18-- http://people.debian.org/~bartm/flashplugin-nonfree/fp10.sha512.amd64.pgp.asc
Auflösen des Hostnamen »people.debian.org (people.debian.org)«... 206.12.19.5, 2607:f8f0:610:4000:214:38ff:feee:b65a
Verbindungsaufbau zu people.debian.org (people.debian.org)|206.12.19.5|:80... verbunden.
HTTP-Anforderung gesendet, warte auf Antwort... 200 OK
Länge: 1273 (1,2K) [text/plain]
In »»./fp10.sha512.amd64.pgp.asc«« speichern.
0K . 100% 130M=0s
2014-02-05 16:17:19 (130 MB/s) - »»./fp10.sha512.amd64.pgp.asc«« gespeichert [1273/1273]
verifying PGP fp10.sha512.amd64.pgp.asc ...
copying /var/cache/flashplugin-nonfree/install_flash_player_11_linux.x86_64.tar.gz ...
verifying checksum install_flash_player_11_linux.x86_64.tar.gz ...
wgetoptions= -nd -P . -v --progress=dot:default -O /tmp/flashplugin-nonfree.xS5MKphHxB/install_flash_player_11_linux.x86_64.tar.gz
downloading http://fpdownload.macromedia.com/get/flashplayer/pdc/11.2.202.335/install_flash_player_11_linux.x86_64.tar.gz ...
verifying checksum install_flash_player_11_linux.x86_64.tar.gz ...
unpacking install_flash_player_11_linux.x86_64.tar.gz ...
verifying checksum contents of install_flash_player_11_linux.x86_64.tar.gz ...
moving libflashplayer.so to /usr/lib/flashplugin-nonfree ...
setting permissions and ownership of /usr/lib/flashplugin-nonfree/libflashplayer.so ...
Flash Player version: 11.2.202.335
moving install_flash_player_11_linux.x86_64.tar.gz to /var/cache/flashplugin-nonfree ...
flash-mozilla.so - Auto-Modus
Link verweist zur Zeit auf /usr/lib/flashplugin-nonfree/libflashplayer.so
/usr/lib/flashplugin-nonfree/libflashplayer.so - Priorität 50
Gegenwärtig »beste« Version ist »/usr/lib/flashplugin-nonfree/libflashplayer.so«.
calling update-alternatives ...
flash-mozilla.so - Auto-Modus
Link verweist zur Zeit auf /usr/lib/flashplugin-nonfree/libflashplayer.so
/usr/lib/flashplugin-nonfree/libflashplayer.so - Priorität 50
Gegenwärtig »beste« Version ist »/usr/lib/flashplugin-nonfree/libflashplayer.so«.
removing /usr/bin/flash-player-properties
removing /usr/share/applications/flash-player-properties.desktop
removing /usr/share/icons/hicolor/16x16/apps/flash-player-properties.png
removing /usr/share/icons/hicolor/22x22/apps/flash-player-properties.png
removing /usr/share/icons/hicolor/24x24/apps/flash-player-properties.png
removing /usr/share/icons/hicolor/32x32/apps/flash-player-properties.png
removing /usr/share/icons/hicolor/48x48/apps/flash-player-properties.png
removing /usr/share/pixmaps/flash-player-properties.png
installing /usr/bin/flash-player-properties
installing /usr/share/applications/flash-player-properties.desktop
installing /usr/share/icons/hicolor/16x16/apps/flash-player-properties.png
installing /usr/share/icons/hicolor/22x22/apps/flash-player-properties.png
installing /usr/share/icons/hicolor/24x24/apps/flash-player-properties.png
installing /usr/share/icons/hicolor/32x32/apps/flash-player-properties.png
installing /usr/share/icons/hicolor/48x48/apps/flash-player-properties.png
installing /usr/share/pixmaps/flash-player-properties.png
end of action --install
cleaning up temporary directory /tmp/flashplugin-nonfree.xS5MKphHxB ...
end of update-flashplugin-nonfree