Lower multires subdivisions turn wobbly in 2.5

Here’s a problem I’ve been having with the 2.5 builds and now with the 2.53 beta. Have a look at the following image. The left is multires subdivision 3, (my highest), the right is one lower. Going lower than maximum does some odd things with the geometry, creating all sorts of weird angles.

http://a.imageshack.us/img816/6835/pleaseworkwithmeheremul.jpg

So am I doing something wrong here? Is there a way to make it work, like it did in 2.49?