MINYANVILLE ORIGINAL Stocks stayed all but flat in mid-Tuesday trading with investor worries over the fiscal cliff balanced by some positive economic data.   The Conference Board revealed that its consumer confidence index rose to a four-and-a-half year high of 73.7 in November from an upwardly revised 73.1 in October. The consensus estimate had been a reading of 73.0   "An agreement to avert the fiscal cliff before year-end remains our central assumption though it continues to look like a fairly close call given the political obstacles to a deal " wrote economists from Goldman Sachs economists in a ...