Got this from the support:
Hello,
We have reached the daily limit for withdrawal that was imposed on us by our bank and all withdrawals are now being queued for processing and all will be processed according to the daily queue and we will keep you updated once processed and we apologize for the inconvenience
Thanks,
MtGox.com Team
This Explaination fits to that was is happening.
The Withdraw robots takes from every User the oldest Withdraw and processes this until the Limit it is reached. Then it stop in the Userlist and starts there on the next run.
So if you have more withdraws in the queue, then it takes long, if you only have one in the withdraw queue, then it goes fast.
It fits to my Experience and to other Posts that i have read in the Forum.
Or maybe somebody else has a different Theorie ?