From UbiquitySyslog.txt which was added to this bug report:
Mar 1 19:08:41 ubuntu kernel: [ 218.493152] SQUASHFS error: zlib decompression failed, data probably corrupt
Mar 1 19:08:41 ubuntu kernel: [ 218.493157] SQUASHFS error: Failed to read block 0x8f96df37: -5
It's possible you had a bad write to your installation media or for some other reason its contents could not be read correctly. If you've tried again and are still having problems you should try re-writing the image to your media (and may be re-download the image too).
From UbiquitySyslog.txt which was added to this bug report:
Mar 1 19:08:41 ubuntu kernel: [ 218.493152] SQUASHFS error: zlib decompression failed, data probably corrupt
Mar 1 19:08:41 ubuntu kernel: [ 218.493157] SQUASHFS error: Failed to read block 0x8f96df37: -5
It's possible you had a bad write to your installation media or for some other reason its contents could not be read correctly. If you've tried again and are still having problems you should try re-writing the image to your media (and may be re-download the image too).