This can indicate a cluster failure, which means that you should re-run.
However, it can also indicate a problem with the inputs. This is fairly common with reported errors. A direct re-run will not solve the problem. Instead, carefully double check the inputs against the instructions on the tool form. It is sometimes even necessary to go back a few steps to find the source of the problem.
If the job still fails after making input changes and/or rerunning, and the problem is at http://usegalaxy.org or can be reproduced there, send in a bug report from the error dataset. Please include a link to this Biostars post in the comments and leave all datasets undeleted (inputs + outputs, even if in error).
Thanks, Jen, Galaxy team