I created a 64x64 px document, at 72 DPI, with an artboard. On the artboard I drew a rectangle covering the artboard, and gave it a 2px stroke aligned to the inside. I then exported it as an EPS file.
When I do that with 1.7.3.481 I get the following when I open the EPS in Designer:
When I do it with 1.8.0.526 Beta I get this instead:
Note the white triangles in the corners, which are not present in the EPS from 1.7.3.481.
my64x64-artboard@72dpi.afdesign
my64x64-artboard@72dpi.eps
my64x64-artboard@72dpi-beta.afdesign
my64x64-artboard@72dpi-beta.eps