this has afflicted the top of only one shoot of the tomato plant. I clipped it off and noticed some aphids and small red bugs under the leaves.

So here's my question. Is this likely to be some incurable Curly Top virus, aphid damage or just nitrogen dificiency due to the new newspaper mulch just starting to break down. HELP! I don't want to lose my best plant(s).

-Ed

I can be more certain if you post an image.

Not so. 2,4-D makes cells grow excessively. See this image from Cornell
http://vegetablemdonline.ppath.cornell.edu/diagnostickeys/TomWlt/2_4_D_Tom.htm

Your description matches glyphosate damage. See this image from Clemson University
http://www.clemson.edu/public/regulatory/plant_prob_clinic/fact_sheet_folder/herbicide_damage.html

You also wrote: "Lesson learned, keep away from cheap spray-on lawn herbcides ..."

Not necessarily so. Any herbicide can drift on the breeze or even just because of the turbulence from the spray. (A breeze is anything that makes the leaves rustle, even the slightest bit.)