[galaxy-user] using lastz

Hi, I have been using Lastz to perform assemblies of 454 data and I have run into a problem where, after the job has been added to the queue, a message appears saying that: Job is waiting to run. It remains like this indefinitely and when I click the 'edit attributes' button, a message says: 'Required metadata values are missing. Some of these values may not be editable by the user'. I am confused since I was able to previously run Lastz with the same samples and parameters and it worked fine. I have tried changing the parameters around a bit but the job still will not run. I would really appreciate any advice anyone could give on how to resolve this issue. Thanks, Neil