New appointments on Outlook 2011 no longer sync via Exchange (but those created elsewhere do sync)

I've searched around for an answer to my problem, but have been unable to find a solution.

For the past few weeks (since the 14.3.7 update-- I think), if I create an appointment in Outlook 2011 on my iMac or MacBookAir, it does not appear on the other computer, nor OWA, nor Outlook 2010 on my Parallels Windows 7,  nor my devices (iPhone, iPad). 

However, if I create an appointment in Outlook 2010 on my Parallels Windows 7, or Apple's Calendar program on my iMac or MacBook Air, or on OWA, or on my iPhone or iPad, they appear on my Outlook 2011 on my iMac and MacBook Air. 

So in layman's terms, it seems that Outlook 2011 on my iMac and MBA cannot push the appointments onto the Exchange Server to be seen by other computers and devices enabled with my Exchange Account, but Outlook 2011 can pull appointments off the Exchange Server if they were created on other devices or programs. 

I removed the Exchange Account in Outlook 2011 on my iMac, and then re-added it back, but it still doesn't work correctly. For some reason, it will only upload about 10 of my 3000 contacts, but I think I can fix that (hopefully without duplicates!).

Of note, I had about 30,000 duplicate holiday appointments, but I deleted those (now have about 1800 appointments). I don't know why they reproduced. They were only the holiday appointments that you can import from Microsoft (and one birthday). 

Appointments used to work perfectly on Outlook 2011, and I suspect the new update may be a culprit. I've been using Outlook 2011 with Exchange server flawlessly since Outlook 2011 came out. 

Any ideas? Thanks.