ArcScene may crash when exporting a scene to VRML if the scene contains a large image displayed in hi-resolution.
VRML export involving image data requires texture resources and memory. The failure occurs if these resources are nearly exhausted before the export process begins and therefore can't acquire what it needs.
Reduce the value on the 'Quality enhancement' slider on the Rendering tab of the raster image layer's Properties dialog box. This will reduce the scene's consumption of resources before attempting to export to VRML.