I found another possible bug I’d like tested in 2.49 but I don’t have it loaded up at the moment. This definitely shows in 2.48 and 2.46:
If a Vector Blur node is used in a .blend, the BI renderer will continue to calculate previous and following frame data, as if for a blur, even when the Vector Blur node is completely deleted and Do Composite is no longer enabled. Of course no actual blur is rendered.
While this is generally a harmless situation, in some circumstances it could lead to large and unnecessary increase in render calculation time, say if a scene has many objects in motion, or massive numbers of particles.
Not sure whether the node tree setup is “respected” even after being deleted, say if the input is via Render Layer nodes, which might restrict the Vector Blur calcs to only those piped to that node. But still, if the Vector Blur node is removed, the renderer shouldn’t continue to act in some ways as if it was.