Greece defaulting on debt would raise EU interest rates magnifying the effects on those indirectly involved

The Bank of Canada is a debtee of financial institutions owed money by Greece and so there's concern that a ripple effect would have wider than anticipated involvement. Canadian financial institutions only have $8 billion in debt owed to them by Greece, Portugal, Spain and Ireland

that compares to $298 billion for UK, $111 billion for USA, $254 billion for France and $370 billion for Germany (Canadian institutions hold a lot of those countries debt though, for example Canadian banks own $94 billion worth of UK debt, $24 billion of French debt and $20 billion from Germany ($138B those three combined). That compares to $521B in American debt held by Canadian banks.(Globeandmail:Canada's Exposure)

Low EU interest rates have in part been a result of the assumption made that it would bailout nations within the union facing fiscal crises (the sheer size of the EU gave the impression that it was more than capable). If Greece proves to be too much to handle how then does it gain back the confidence of investors when it has yet to deal with Spain and Italy? Higher long term interest rates would be inevitable and that alone would have broad, global consequences which would make cheap credit a thing of the past.