Globe and Mail Update The year-old credit crunch has become a full-scale financial crisis that this week alone has seen the collapse of a major Wall Street investment bank, the sale of another and a move by the U.S. Federal Reserve to bail out a private insurer to the tune of $85-billion (U.S.). Four Report on Business reporters explain what's behind the global shockwaves. Why are credit markets frozen, and why won't banks lend to each other? Credit markets have dried up because lenders fear they won't be paid back. Fear of the unknown has caused banks and other institutions to hoard their money. Worry that more financial institutions will fail has made banks reluctant to lend to one another, exacerbating the situation and raising the chance that another bank will find itself without enough funds. It's unclear to what extent individual financial institutions are exposed to the toxic assets that caused the crisis. For that reason, they are only willing to lend t...