The Humax5400Z has "block"in the bootloader which prevents you loading new software. But that can be got around using a JTAG interface or Z-board. Read older posts on this board for more details (or follow some of the links in the posts). The search function here can help you locate 5400-related posts.
MY DEAR CHK THE SITE WWW.UPLOADFLY.COM I DON'T THINK THE SOFTWARE IS LOCKED OR ELSE. I AM REGULARLY TESTING THIS RECEIVER . EVEN THAT I HAVE TRANSFERRED THE 5400 SOFTWARE IN THE Z MODEL AND IT WORKED WELL.U CAN ALSO CHK THESE SITES WWW.LAURALS.COM AND FOR THE OLD TOHS WWW.TUXONHUMAX.BERLIOS.DE.
I HOPE U WILL FIND ENOUGH MATERIAL THERE.
And One More Thing I Have Never Ever Used A J-tag. What Ever U Do With This Receiver It Is Not Dead. Just Replace The Downloaded Software With A Right One. Thhhhaaaaaaaaats Why I Looooooove This Receiver