I upgraded to the latest version of Unity on my Mac, one thing I noticed is that the explosion textures (shoot a barrel) are messed up (looks like it is ignoring the alpha channel as the explosions are now showing as rectangles with black where they should be transparent). Is this due to a bug or did they simply mess something up with the demo that is included with the install?
Check the materials being used for the explosion textures (this is for a particle system, right?) It may be that the shader references have been lost or changed somehow.