EXT3 could not be found on device hdb1 (bootpartition

[Super Donkey]

When I boot up I see the error message: ext3 could not be found on the
device hdb1, which is my Ubuntu boot (root partition).

The boot works fine from that point on, well I notice nothing. I made all
my partitions reiserfs.

I'm wondering why I see that message scrolling on the screen and what
consequences it has. Shouldn't the filesystem not be hard coded into the
distro/os?