(Co-founder of Bitonic here.)
This is not unusual for Dutch banks, ING in particular. Although we as a company have good relations with them (as a long term customer), transactions to/from bitcoin are still considered high risk by them.
Automated systems still sometimes block transactions to us, contacting your bank (ING mostly contacts you, other Dutch banks mostly don't) and asking them to deblock almost always works.
If you keep experiencing problems, please contact us so we can address these issues with the bank directly.
With rabobank I never had any troubles purchasing at bitonic.. (maybe at the end of November 2013 it was a bit difficult).
Thanks for providing this great service! Buying bitcoin was never easier

I have ING, never any problems before. Allways on time, even faster then most of my friends who uses different banks