iPhone 3GS everything syncs except PC calendar events

iPhone 3GS v6.1.2; iTunes v11.0.1.12; PC Windows 7 & Outlook 2010. Sometime during my trip (HI > NV > TX > HI) my iPhone and Outlook calendar stopped syncing.  Everything syncs except the calendar events; even the birthdays sync.  I only have one PC calendar and one iPhone calendar.  When I use the Advanced - Replace information on this iPhone - Calendar feature, the result is only Birthdays appear on my iPhone until I manually select the calendar under From My PC on the iPhone.  It is as though iTunes isn't recognizing the iPhone calendar.  Every test to add or delete an event from either the iPhone or PC calendar does not get sent to the other device.  The usual iTunes sync error allowing me to select which event is correct never appears.  Any and all ideas will be appreciated.  I've spent several days reading through the various "sync" issues posts to no avail.  I'm sure it is something I did incorrectly trying to resolve the issue but ...