Sauce of mystery

Anyone explain this mystery?

A couple of weeks ago I followed a recipe from Andrea Antona's excellent Modern French Cookery book that combines shallots, red wine, fish stock, double cream and butter to make a fabulous (though I say so myself) full-flavoured sauce.

This weekend I followed the same recipe, but (before adding the cream) tasted the liquid and it was so metallic it ended up in the sink.

The only difference was that I used a wine made from syrah first time and a pinot noir the second.