IT Arrears Notice-After 18 Months

Hi!
For AY 2007-08 I'd paid IT of Rs 24, 000 on March 24, 2008. That's the date of the receipt. The return, digitally signed, was E-Filed on March 31, 2008.
Now, on Oct 3, 2009 I received a postcard informing me to produce a challan for Rs 5554 for Ay 2007-08. That's it, nothing else. The postcard bore the seal of the local ITO and was dated Sept 24, 2009.

In mid-November I received another postcard with the same details and, again, the date on the postcard was Sept 24, 2009. Asking me to produce a challan for Rs 5554 concerning AY 2007-08.

A week after that I received an Ack Due SpeedPost communication which informed me very clearly that I had to pay IT arrears worth Rs 5554 on or before Nov 30, 2009.

Needless to say, I've ignored all 3 communications. Not that I've anything to hide or I'm petrified of the option of facing the ITO. I know very well that I can be targetted and harassed.

I've not received any email intimation of any tax arrears. The form 26AS that I have received through email in October does not hint at any tax arrears for AY 2007-08.

I'd asked the guy who prepared my balance statement for AY 2007-08, a lawyer actually, to follow up on the notice with the ITO and he informed me that the ITO was quite adamant about it and I'd no option but to pay.

I asked the lawyer who prepared my balance sheet as to how a notice for IT arrears appears after or equal to nearly 18 months of my filing my returns could be sent by the IT Dept. (Pl note that I have mentioned that the 2 postcard notices clearly mention the notice date in seal as Sept 24, 2009. The SpeedPost notice is dated Nov 1, 2009). He could not come up with a lucid response to that.

The Excel balance sheet and the Statement showing the tax payable have been attached with this email. I can also upload the actual XML that I uploaded during e-filing on Mar 31, 2008. (It looks like I can only upload 1 file per post here, so if some members are interested in the actual XML filed, I can send/upload that too)

I did the math and discovered that I have indeed paid the proper amount of tax as per rates for AY 2007-08. How come I have been asked to pay Rs 5554 more? Does the IT Dept have the proper authority to notify an assesse's tax arrears even after or equal to 18 moths from the date of filing/e-filing? If I have to object, on what grounds do I have to object?

Please do let me know your opinion.

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Best Regards
Suresh