In order to claim the long time homebuyers credit, the law requires that for a married couple, both the husband and wife satisfy the prior ownership and use requirements. That means that both you and your wife would have had to both owned the condo for at least 5 years, plus you must both satisfy the use requirement of having lived in the condo for a period of 5 consecutive years out of the last 8 years immediately preceding your new home purchase.
Even though your wife may have lived in the condo for 5 years, if she was not also an owner of the condo for that same 5 year period, she would not qualify for the credit. Both spouses must qualify before either spouse can claim any part of the credit, so filing a separate return would still not allow you to claim the credit for the home you purchased in 2010.
I am sorry I could not give you a more favorable answer, but those are the rules that the IRS has set in place.
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