Data management error?
 

I am writing an Excel VBA application and ran into an problem that has the symptoms of a memory overwrite. The sympton was a stop by the debugger on a line that was taking a square root of a negative number. The number was very small (10^-16), negative, and wrong. While tracing through the program I discovered that this answer came from a previous calculation involving multiplying two numbers together, both of which were close to 1. The answer was this small number

As far as I can tell, VB is very good about keeping me bounded within my data arrays, though I am using ReDim to size storage areas based on the problem at hand. The error does not occur until a get to a certain size of problem.