http://www.pasteall.org/blend/1464

To reproduce it, just open the file and press F12 to render the scene.

I've experienced another bugs but I can reproduce them again so...
Any way ther's a strange one in the new tool shelf-panel, I think. The truth is out there.

Blender 2.5a. Windows XP Pro. , Mobile DualCore Intel Core 2 Duo T7250, 2066 MHz (11 x 188), Inst. set x86, x86-64, MMX, SSE, SSE2, SSE3, SSSE3. NVidia GForce 8400M G.