Yes.
Effective October 2008, banks and credit card processors may no longer board merchants that use software that cannot be validated as PABP or PA-DSS compliant.
As of July 2010, merchants (including restaurant operators) are required to use only Visa PABP or PCI PA-DSS validated point of sale and payment applications.
Some financial institutions are already enforcing the requirement for an annual PCI security self-assessment and quarterly network scans, and levying fines for non-compliance. If your POS system is non-compliant after the July 2010 deadline, you will automatically fail your PCI assessment, and could lose the ability to accept credit cards.