If you updated your SGE installation from a version prior to 6.1, you may have noticed that when you use the qstat command, only your jobs are shown. This is the new behavior of the qstat command.
In case you want to view all jobs, just add "-u *" (without the quotes) to the $SGE_ROOT/$SGE_CELL/common/sge_qstat file, which will change qstat behavior for all your cluster or to do the modification for a specific user, create a $HOME/.sge_qstat file for that user, adding the same content.
That will produce the same result as execute the qstat -u "*" command.
You can learn more at sun.docs.com and at DanT's GridBlog, from where I've found that information.