Problem is I think that the plugin does not like the TZID Eastern Standard Time. It is not one that is used by php http://www.php.net/manual/en/timezones.america.php
Php prefers America/New_York
The ics spec RFC5545 uses those examples eg: DTSTART;TZID=America/New_York:19980119T020000
The spec is a bit vague here http://tools.ietf.org/html/rfc5545#section-3.2.19 in that it doesn't insist on a naming convention, but suggests using the Olson db.
Your ics file,produced by microsoft, and is generating dates like:
DTSTART;TZID=Eastern Standard Time:20120818T000000
It seems microsoft has ignored the suggestion
Google is probably fixing up the timezones and issuing the commonly accepted olson db tzid's.
The plugin does have some funky logic to try to make sense of most timezones, but is spewing on this one and ending up with London, which of course then throws the times out
So if you use an ics generator thats use olson TZID's (or amr-events :-) ) then it should work fine.