A little bird told me it's because they still use cobol fixed width data and are basically scared to change it. To fix, first they have to finish their rewrite.
Changing a legacy mainframe COBOL system shouldn't be scary. Provided you have qualified staff and the right tools (such as COBOL static analysis tools), it is not inherently more risky than changing a Java or .Net app.
So ING sold it off to The Bank of Nova Scotia (BNS).
Canada's bank-friendly anti-consumer policy meant that ING Direct had some value, and BNS coughed up the most cash.
They were only allowed to use the orange ING branding for a few years, so they changed it to something that was borderline familiar: an orange fruit.
BNS probably had to, or chose to, switch ING clients over from the Dutch back-end to their Canadian one.