The queue that runs mapping jobs is known to be very busy right now. Our administrator is keeping close watch over it.
The best strategy - and this is for all jobs - is to start them and then allow them to run to completion. This preserves the job placement in the queue - and is the most effective strategy for getting work done on the shared public resource at http://usegalaxy.org and likely most other Galaxy instances.
If your work is very urgent, a cloud Galaxy may be an alternative. Please see: http://usegalaxy.org/cloud
Thanks for asking! We are aware that other users are probably also curious about the delay and hopefully this helps to explain that it is known, due to a peak usage period, and how to execute work.
Jen, Galaxy team