Income Tax interest implications under Sec 234 A, B,C

One of my client could submit his returns for AY 2007-08 on March 31, 2009 whereas last date for filing returns was July 31, 2008. Although he paid full income tax as TDS before March 31, 2008 and there was refund due in this case. However, the income tax authorities have slapped a notice under Sec 234 A, B, C and asked for interest payment. Can some one advice how to reply to this issue. Appreciate your expert advice. thanks