You can turn off the power to the boiler at the circuit breaker box. Then check every connection, wire-nut or otherwise, from the circuit breaker box to the furnace. Are there any other loads on that circuit? Most furnaces/boilers like to have a branch from the main box all to themselves.
See if the location of the 8610 is such that it can get very hot when the boiler is operating. Heat kills electronics and many ignition modules die a premature death do to poor location by the designers.
Is there any other appliance in the house that, even if on a different circuit, draws a large start up current? I am thinking mostly of a very large motor... water pump, especially if 120 volts, or anything that could cause a house-wide voltage drop (you'll notice the house lights either dim or get brighter when the load starts) that could cause the transformer secondary voltage to drop enough for the error. How is the service drop to the house? Are you in a salt air environment? Possibly corroded connections at the power company's transformer is causing the neutral to float.
If all the basic 120/240 service to the house seem to be healthy I think you may have a sick s8610. You can replace the transformer first, if you like... it'll be cheaper, and see if that helps.