Sunbird: Can't use function "none reminder"

When i create new event from program i choose no reminder in Reminder: option

But program save it into reminder 1 hour before.

I change it to no reminder but program save it into 1 hour before again.

I change it to 5 minute but program save it into 1 hour before again.....

PS. WinXP sp2 (Original) use on my harddisk and i sync data with google calendar. (if i create on google calendar with no reminder in program can sync to no reminder)

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