Cron jobs unreachable are cron jobs with URL that SetCronJob can't open a connection to its host. This may be caused by its host is not valid, domain name expired (dropped), its firewall blocked SetCronJob, or slow internet connection, etc.
For example, you set a cron job every 5 minutes with URL like http://unreachable.example.com/backup.php, and SetCronJob can't connect to unreachable.example.com within 2 seconds.
From July 15, 2009, all cron jobs unreachable will be deleted. This is an automatic process, and will be run every 5 days, at 07:35 AM GMT. So, the next execution should be at July 20, 2009, 07:35 AM GMT.
This is to save resources to execute other URLs faster, as cron jobs unreachable will take 2 seconds for nothing.
When your cron jobs are deleted, you'll received a message from SetCronJob. You can re-check whether your cron jobs are unreachable or not by go to that URL, set cron job with that URL, or check with web-sniffer.net, adfreeproxy.com, phpmyproxy.com.
If they're OK, please reply that message to inform me. I'll be appreciated for that.
Sorry for any inconvenience, and thank you for reading :)