As you mentioned, also my "cheap" 1GB usb stick has random problems, but my SanDisk 4GB "Cruiser" USB stick works fine...
Try another USB stick.
I am getting a second Deneb for my A4000T. I just moved my original one over to my A4000D which is running OS4, and after some trial and error, I have loaded the OS3.9BB2 patches and SmartFileSystem into the flash so they are available at startup. OS4 reboots the machine once the OS4 kernel is loaded so you have to change some options in Luciferin when you flash your Deneb...and you have to exclude Luciferin from Petunia (JIT), but it works
