Who said global? A localized loss of power or connectivity for a substantial time period is not necessarily catastrophic. But there still has to be some exchange of goods and services both within this locality and between it and the outside world.

Without some accepted medium of value exchange between an electronically disconnected region and the outside world, it becomes much more difficult to establish or restore connectivity. So the purely cashless system is actually much less robust with respect to physical failures.

Maybe not catastrophic, but personally I can't stay where I live (in the city) with more than about 48hours without power, as I can't safely store food and I can't really get new food (unless the loss of power is only at my place).

Anything less than that, you use batteries.

I'm guessing you eat a lot of meat and/or fresh produce? There are plenty of foods out there which keep for longer than 48 hours: canned foods, crackers and other dry goods, and so on. They might not be as tasty, but keeping a decent food supply doesn't really require constant refrigeration.

The point about cities I'll give you to some extent: a city with very high population density is generally dependent on a much larger total rural area which supplies them in exchange for economic support. If the loss of power also kills all transportation, you're doomed. But our current transport infrastructure generally includes autonomous non-electric options even where public transport is primarily electrical (trains etc). You can pay someone to bring you food from outside the city without needing a network connection.

Really this reinforces my point above about currency though: absent an uncompensated intervention (ie government), a city which loses its power and connectivity must have some medium of exchange to pay for its food supply to be transported in, and to get itself back on its feet. Some non-electronic medium (ie cash) is essential in these cases.

Two weeks? You are making the common "predict the future" mistake of assuming people will not try to do anything, and will just sit around. In actuality if there was a global loss of power people will figure out many many things to help.

Maybe, but without electricity, how are you going to transport, prepare and store food?

Propane.

Propane powered vehicles, propane fueled fire, propane refrigeration.

...and there is this (A Solar Ammonia Absorption Icemaker): http://homepower.com/article/?file=HP53_pg20_Vanek

Now all you need is a way to power your currency.

Speak for yourself, fella.