My sister passed on 6/24/12. She opened a new account on 6/8/12 (401k) naming me the benificiary. Will her husband have claim to the account?

My condolences to you on your loss. If your sister designated you as the beneficiary of her 401(k) account, but she was married, her husband would need to consent to that beneficiary designation. For an IRA account, that would be different. However, a 401(k) account is controlled by a set of federal laws known as "ERISA." ERISA says that a participant's spouse (a participant is the person who the 401k account belongs to) must be the beneficiary of the account unless the spouse consents to another beneficiary designation. Therefore, your sister's husband may end up with rights to the account, even if you are named as the beneficiary. You should contact the plan administrator for the 401(k) account. You may also want to contact your own attorney, and have the attorney review any documents you may have relating to the account. It may be that your sister rolled her 401(k) over into an IRA after all, in which case the ERISA rules should no longer apply to the beneficiary designation. But without being able to see all the relevant documents, it would be impossible for me to know exactly what you have.