That's still a division by zero error. Division by zero is no more valid in engineering than it is in mathematics. While I was out on a walk in my neighborhood I thought about the practical engineering problem you first mentioned above: whatever kind of resistor you are talking about, I think a lot less than infinite electricity could jump the gap filled by any finitely sized resistor, even if you initially regard it as having infinite resistance for purposes of analyzing the circuit. But I will leave further discussion of this point to readers here who have formal training and experience with electrical engineering, as my childhood best friend does. I'm not aware that he considers infinity a number or that he puts it anywhere on the number line.

http://mathforum.org/dr.math/faq/faq.divideby0.html

http://mathworld.wolfram.com/DivisionbyZero.html

http://en.wikipedia.org/wiki/Division_by_zero