please also remember to upgrade the jloader (bootloader) on the switch as JunOS version above 10.4R3 required this to boot.
Refer to https://kb.juniper.net/InfoCenter/index?page=content&id=TSB15524&smlogin=true&actp=search for instructions on how to upgrade the jloader.
As others has stated, please verify the md5/sha1 checksum of the image. Can be done via the command "file checksum md5 /var/tmp/image-name"
Example:
jh@fw> file checksum md5 /var/tmp/kmdchk.log
MD5 (/var/tmp/kmdchk.log) = 5c2b1194b54edfd0fc06e47d3793b1e3