Apparently vertex textures are totally broken. As soon as vs_3_0 shader tries to compile a shader with a vertex texture fetch, my PC resets, no warning, no blue screen of death.
e.g. code in vertex shader
float rtex = tex2Dlod( textureSampler, float4( coords.xy, 0.0, 0.0 ) ); //must use tex2Dlod in VS