[w i l l]

Could someone tell me what these are?... I've never seen them before.

They're in the bottom left corner of the mxcl viewport.... a white and grey circle with an 'R' and 'A' inside.

[JDHill]

That would mean you are rendering the Render and Alpha channels - just click on the icons to switch the display.

[w i l l]

Oh nice.