Another frustrating problem I've encountered in Maya 2013 is trying to delete an custom attribute in the AE and it won't delete (even after right clicking and selecting DELETE ATTRIBUTE).
A simple way to solve this problem is to just click LOAD ATTRIBUTES, and sometimes when that doesn't work (ugh Maya, ugh..) click COPY TAB and then everything should be refreshed, so right clicking and selecting DELETE ATTRIBUTE will work fine.

Colby