Travisa just repeated what they told me yesterday. I tried to call the Russian Consulate in Houston and was forced to leave a message.

In the meantime, I noticed this paragraph on the US Department of State which can be interpreted more than one way at http://travel.state.gov/travel/cis_p.../cis_1006.html

Transit Visas: If you intend to transit through Russia by land en route to a third country, you must have a Russian transit visaissued by a Russian Embassy or Consulate. If you are transiting through one international airport in Russia, and will depart again in 24 hours to an onward international destination, without leaving the customs zone, Russian law does not require you to have a transit visa. However, this law is sometimes misinterpreted by travelers and customs officials alike, and we recommend you obtain a Russian transit visa if there is any doubt about your transit plans. Foreigners who arrive in Russia without a valid visa, who do not meet visa-free transit requirements, may be forced to return to the point of origin at their own expense.