I can't speak for cpuminers but i have the same problem on poolinat0r.com
The problem i found is a timeout on the payout runs. From time to time the payout cronjob is running very long, i wasn't able to track it exactly down. After the cron is running in a timeout, the payouts are getting auto disabled. This is for security reasons.
After the payouts are getting disabled (the stratum/mining proxy is NOT affected by this, shares/miners are safe even payoutcron is disabled) they have to be reenabled manually, after checking the error log, wallet and sql database.
I never had any "real" problems on poolinat0r.com yet, it's just that miners have to wait a bit. I have email notifications for failed/disabled cronjobs so i can check them.

poolinat0r.com has had that problem again today. I already have reenabled it.
If Anthbs needs some help, he can contact me here and send me a PM.


Regarding the 10VRM minimum withdraw limit: i also have set it to a minimum of 10 VRM because of the transaction fee of 0.2VRM. If pools would lower the limit to let'say 2 VRM, the miners would only receive 1.8VRM, meaning 10% are lost for transaction fees.
So the limit could be lowerd, but it's not a good idea to waste 10% of VRM i think :-)