Updated to 1.5 piwik and ran into a cron bug.
The shell script archive.sh runs piwik code plus some zend code that requires ini_set to be enabled. Most hosts have this disabled (or should) and as such, the shell script fails.
The fix is:
Copy/paste your ini file from your root dir to the misc/cron folder - edit to remove ini_set from the disable list
then in the cron/misc/archive.sh file, find replace
$PHP_BIN -q -c /home/FULL PATH TO/www/piwik/misc/cron/php.ini
I think there are a half dozen instances.
This tells the command line to load your edited ini file with ini_set allowed and lets the script run.