I'm guessing that /usr/sap/trans is local to your system. it's probably an NFS mount. Check security of files, directories and NFS mount.
all you need to do is get the log from /usr/sap/trans/logs and copy it to /usr/sap/trans/tmp and all will be OK.
if above two things do not work then try to debug transport program and then retry the same transport it should succeed.