Mathematica 10.0.2.0, specifically:
10.0 for Mac OS X x86 (64-bit) (December 4, 2014) ReleaseID 10.0.2.0 (5206630, 2014120404), PatchLevel 0
appears to have a bug in handling boxes. The application crashes pretty consistently with the following:
A cell with Style DisplayFormula and contents:
Copy the cell and, in front of the b, type Keyboard Entry [Esc]ee[Esc][Ctrl] to produce formatted e, the base of the natural log raised to a power. Note the ghost box in blue to the right of the true box for the power. Attempt to enter the power in the true box and ... crash.
This is small, specific and reproducible so may help uncover a bug.