The First Part to Break on my Reprap Mendel

When I started a print today I was confused to see the first layer of plastic getting squashed down very flat, so that it was noticeably thinner at one end in the Y-axis. When I stopped this and checked what was happening with the extruder movement, it seemed as though the bed had lifted up at one end, which was confusing since there was no way for the sprung bolts supporting the bed to have unfastened with nylock nuts on them.
However, upon investigating a strange rattling noise that I was hearing on the opposite side of the printer, I found this:

y-bearing-180-outer-right

X-Axis Improvement Update

Having printed a few Prusa Mendel parts since modifying my x-axis, without changing any settings, I have now seen a very slight improvement in accuracy:

Left: Greg's Hinged Wade's Extruder Idler turned out the best I've printed yet, where the top-most section forming the hinge can sometimes be troublesome as it is such a small area, Right: Z-Motor Brackets have a slight blemish on the inner surface, but no layers going significantly out of line

Mendel X-Axis Upgraded

Difficult to see here: M3 nut torn away plastic around it, as its slot was too shallow to pull it out of the space the bar goes through, so put too much torque on it trying to squash plastic

So my original x-axis modification design didn't quite go to plan as I found a couple of weaknesses in the prototypes, which didn't print brilliantly in the first place, but after putting wider tolerances in places, for instance making the spaces next to the smooth rods for M3 captive nuts 1.5 times as deep as they should be, I arrived at something much more robust.