LTSpice Error: timestep too small
Your simulation is, for some reason, too hard for the solver.  See this page for some guidance.

Simulators like this use numerical ordinary differential equation (ODE) solvers. Nearly all such solvers adjust the time step dynamically, trying for the largest possible time step while maintaining accuracy. So the time step gets small either when you're doing something that challenges the algorithm (like a stiff system), or when you're asking for too much (like the relative tolerance that @jrive) spoke of.

Things to try are to: 


First, look at your schematic and ask yourself if you've just asked a nonsensical question
Second, try changing the solver.  I'm not in the same room with an LTSpice application, but AFAIK it uses a Runga-Kutta solver, which doesn't do well with stiff systems (Google "stiff system simulation" for details).  My favorite go-to in this case is the Gear solver.  It is (I think!!!) in a menu selection marked "controls".  They may also have a minimum time step that you can specify, at the expense of possibly screwing up the accuracy of your results.