Thanks Joel. I thought it was working because no gl error was returned.
I also read this in the specs:
void TexBufferEXT(enum target, enum internalformat, uint buffer);
is equivalent to
TexBufferRangeEXT(target, internalformat, buffer, 0, size);
with <size> set to the value of BUFFER_SIZE for <buffer>.
The number of texels in the buffer texture's texel array is
floor(<size> / (<components> * sizeof(<base_type>)),
where <components> and <base_type> are the element count and base data
type for elements...
But I will try to split the attributes to two Vbo's and two BufferTextures then. Thanks.