Capital is still a living thing, and as such, requires constant circulation and movement to prosper and survive, even as it fixes and freezes the movement of its own constituents to organize its various functions. Like cells, businesses live and die all the time, and then are renewed by the fresh growth of upstarts, but disruptions of movement on a great enough scale and capital can just about go into cardiac arrest or something similar.
We don't see this so much today, but the general strike can bring whole logistical systems to a screeching halt, causing cascading crises down the line, such as in the political and financial systems. This is a crisis of production that is peculiar to the era in which industrial capital was dominant of course.
No, today we see many more crises arising in the financial sector, which is all too appropriate for a financialized era. These expanding and popping bubbles can do massive damage on their own, and raze whole industrial sectors and populations.
The crisis lies in the halting of circulating of commodities and currency. If businessmen stop doing business and warehouses close their doors and hoard money pools up, then workers aren't being paid and goods aren't going to market, and entire populations - being wage laborers - are deprived of essential resources to survive, at least peaceably.
We depart from the body metaphor though, as capital is peculiar in its movement in that it must constantly expand and consume more energy, or else it is becoming seriously unstable very quickly.
