I've never heard any claims that the 41 billion will just disappear. The worst I've heard is that they will restructure the loans to extend pay back dates.
Also, from the article, the banks have a drop in the bucket exposure to these loans, which isn't even reporting in their annual reports as a risk. The highest exposure bank seems to be half a billion on BoA's balance sheets, and like I said, it isn't like that debt obligation is just going to disappear.
There's a lot of FUD around Greece "defaulting", and like I said, I think the main impact area will be the stock market, not necessarily bank balance sheets or the economy at large.