Has anyone noticed that the scripted invis prims of shoes that everyone in SL uses now shows up and never properly loads to alpha?
Here is an example:

As you can see, the shoes look like the script hasn't finished loading or the prim hasn't finished rezzing (how shoes used to look before rezzing) However, these never seem to rez. I have tried many different shoes, from many different creators.
Other than the obvious sarcastic answers (ie - dont wear shoes, etc)

Edit:
I figured out what it is, it happens when you stand on mega prims!