issue during color conversion (NV12 - RGB)

[Guetcho Guetchev]

Dear Gstreamers,

I have the following pipeline (Gstreamer 1.0.5): 

appsrc caps=video/x-raw,format=NV12,width=480,height=640,framerate=20 ! videconvert ! capsfilter caps=video/x-raw,format=RGB ! appsink

A sample of the resulting image can be observed here: http://imageshack.us/a/img802/5821/image068.png
I am pretty sure the input image is correct, because it comes from an iPad camera. For the more curious the native pixel format is a bi-planar component Y'CbCr 8-bit 4:2:0, video-range (luma=[16,235] chroma=[16,240]).

The question is: what might cause the left border disturbance? Also, please, notice the upper left corner is totally garbled. 
Any ideas?

Best regards,
Guetcho