I had the same problem, and I've resolved :
First, install busybox :
With telnet : opkg install busybox-cron
With an editor, type :
#!/bin/sh
rdate -s time.mit.edu
Then Save as TimeUpdate.sh, in /etc/cron/scripts
With an editor, type :
*/1 * * * * /etc/cron/scripts/TimeUpdate.sh
Then Save as root (without extension), in etc/cron/crontabs
In etc/enigma2, edit the file settings and add this line :
config.misc.useTransponderTime=false
Save it, then unplug the power (not a proper shutdown)
That's all