if they were dismissed, there is no real record of what they were. you can
try looking at the Modified field to see if that helps to identify the ones
you dismissed.
http://www.outlook-tips.net/archives/2004/20041203.htm

try starting outlook with the cleanreminders switch - this should help with
the new reminders you set not working.
http://www.outlook-tips.net/beginner/switches.htm

finally, if you do this often and for whatever reason, choose to use the
windows time /date applet instead of outlook's calendar, one of the tools
here will prevent such problems in the future:
http://www.slipstick.com/calendar/timezone.asp - the first 2 have calendars
that are easy to access, I forget if the others do.  (Vista includes a tray
calendar and hides the time & date changer.)