Operating system and graphics card
Broken: blender-2.75-d39e188-win64 (all recent builds)
Worked: blender 2.75a
Blender randomly crashes while editing mesh with subsurface modifier (for example "merge vertex"). Deleting subsurf modifier stops crashes.
However this problem hard to reproduce from scratch, this bug appears after some time you start working.
See attached file.
There is also a strange thing about this crashes, if you load this file with UI enabled, then edit mesh + merge vertex = crash,
load it without UI = everything if fine for a wile, after some time crashes reappears.
Tryed it on 2 computers win7x64 and win8x64, factory defaults, even deleted C:\Users\***\AppData\Roaming\Blender Foundation\Blender\2.75 folder.
Blender 2.75a opens that file ok, no crashes.