Nobody panic (yet), this may be a false report from the arm mkimage tool!
Code:
$ gunzip main_kernel-5.1.0.img.gz
$ file main_kernel-5.1.0.img
main_kernel-5.1.0.img: u-boot legacy uImage, Linux-2.6.31-rt11-lab126, Linux/ARM, OS Kernel Image (Not compressed), 5173248 bytes, Wed Apr 4 22:41:49 2012, Load Address: 0x70008000, Entry Point: 0x70008000, Header CRC: 0xD06DD1C2, Data CRC: 0x723AAEFD
$ mkimage -l main_kernel-5.1.0.img
mkimage: ERROR: "main_kernel-5.1.0.img" has corrupted data!
That message is coming from u-boot/tools/default_image.c when it does a crc32 on the data area.
I don't see anything wrong with the code ...
(and the 64 byte header already passed the crc32 test)
Will be taking a closer look at this.
Since I want to re-use parts of the tool sources for an un-make-uImage tool.
Edit:
Theory #1 - This kernel image file was bspatched to 5.1 in the field from an earlier version and our friends at lab126 did not bother to also bspatch the crc32 checksum to match.