Before reporting problems, please check the following information. It could be very useful. 

• condor_q -better-analyze -name sn-02.cr.cnaf.infn.it <cluster id>

• condor_q -pool ce02-htc.cr.cnaf.infn.it:9619 -name ce02-htc.cr.cnaf.infn.it <cluster id>
• grid-proxy-info. Is the proxy valid?
• voms-proxy-info --all. Do you have the right/valid proxy extension?
• If available, output and error.
• Estimate needed RAM. Is it compliant with queue resource?
• Estimate job duration. Is it compliant with queue resource?
• Check queue status. Is the queue full?
• Estimate the size of input (output) sandbox. Are actually they compatible with what you expect?

Once you have checked all and you do not get hints about the problem, please report the problem to User Support group.
When reporting problems to User Support group, in addition to the previous ones, try to provide as much of the following information as possible:

• Grid/local job id
• Submit description file of the job
• Has the job particular requirements?
• Which is the executable?
• Which is the scripts?
• Is job trying to read data somewhere through posix?
• How long has the job been running/waiting?
• Which OS is the job using?