Minecraft or Bukkit bug? world randomly corrupted

hi guys, i'm not sure whether what's happening is caused by bukkit or minecraft itself.
i'm currently most of the time far from my original spawn point in another area of the world. i noticed some time ago that there suddenly was a birch in the middle of where i'm in most of the time, while i started to be there before the update growing birches was out. below it, there was some weirdly sharp geometry, however, i didn't pay much attention to it.



today, i revisited where my first spawn point was and noticed a lot of these weird cuboid-shaped chunks of blocks being randomly placed or cut out. some of them are placed on top of my stuff and others deleted them. i'm glad it didn't hit anything big yet, i'm afraid it might at one point though.

since the problem is hard to describe, here's some screenshots (click to enlarge):





there's also going on some weird stuff where the problem happens on one side of an edge and suddenly changes to the other side. sorry, my english prevents me from describing it properly, so here's some screenshots trying to show what i mean:

turning the camera around
and in some cross-way here:


it seems to me that certain parts of the world could not have been loaded and thus are just generated again. i'm currently using craftbukkit #99, however, i'm not sure which build i used when this happened since it might have when someone else revisited that area. i'm also using the General, WorldEdit, Teleplus, MyWarp, MyHome, MinecartMania and MagicCarpet plugins.