The answer depends on the language of the sublease. If it is truly a term that ends October 2010, the term ends and you should be able to leave. If there is language that says "and month to month thereafter" it may be more problematic. In that case you may be held liable for 60 days from either the date of notice or from last day of October (e.g. End of December). This also depends on the language in the sublease document related to the 60 day notice.
I agree with Mr. Glosser and would add you should speak with your landlord and negotiate a termination agreement. If the lease truly terminated you can go. Get everything in writing before it gets out of hand.
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Just writing to add that its important not to confuse "being in possession" with "paying rent". Commercial landlord tenant agreements are purely creatures of contract, and they can create whatever terms the parties want. Giving 60 day's notice is a term. It isn't great, but there it is. It doesn't mean you cannot leave, it just means that you are likely going to owe an additional month's rent.
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