It's not rows or columns. Most of my variables are called out as integer, double, boolean, etc.

I'm not sure a code sample would help:
- It bombs at different places with different input
- It bombs at lines that were successfully executed many times before
- It bombs on simple statements with all values in their correct ranges
For example:

Sub GetTemp()
' Sub GetTemp(j, q1, q2, u0, u1, u2, zz) '--thermal response
' fluxes q1,q2 temps u1,u2 step zz t(eq) u0
bb = (Abs(ae(2, j)) + ae(1, j)) * sig
u0 = (q2 / bb) ^ 0.25 ' <---BOMBS HERE
u3 = ut(j) / bb / ((u1 ^ 2 + u0 ^ 2) * (u0 + u1))
....
All variables in uo= ... double and in range and most transmitted by Public statements.
By changing the timestep from 5 to 4 , it bombs at the next statement: u3 = ....