The problem happens when you render image from any part of UI except 3D viewport.

How to:

1). In a new scene add particles to Cube, set particles count to 30000.
2). Duplicate Cube couple of times and set camera to fit all cubes. Play some animation.
3). Now, select any cube and press '/' to isolate it.
4). Render it. It will be ok, but if you render it again, in Image Editor, you will see all cubes and particles. Same happens after you press render button while your mouse out of 3d view.

OS:
Ubuntu 10.4 x64
Windows 7 Ultimate x64

Blender 2.63 (2.62 also)
rev: 45996