--- Operating System, Graphics card ---
win 7 64bit gtx 560 ti


--- Blender version with error, and version that worked ---
works for blender r53189 ,does not work in blender r54265 or r54002 or r53672

--- Short description of error ---
BI render doesn't appear to recognize alpha channel

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---

1.Open default scene with cube hit f12 (blender render)
2.Go to compositer/node editor and check use nodes
3.The image in the renderlayer node should display the cube with a transparent background (checker pattern).In official version r53189 this works fine.In more recent builds I can't seem to be able to get a transparent background,It appears as default grey background.

didn't include blend file,as it is just a default scene + f12 that is necessary