so, i tried all of the posted solutions on my nexus 7 and none of them worked for me, but here's how i eventually got it to work. i logged into the calendar from my laptop, exported the events and imported them into a newly created calendar. syncing the newly created calendar to the n7 worked. i then went back to the computer and deleted all of the events from the first calendar that wasn't syncing and reimported all the events to it. tested the sync on the tablet and they showed up. i then deleted the 2nd calendar that i'd made. i also went to the accounts sync on the nexus 7 and the spinning sync icon disappeared after i went through all of these steps. seems to be working fine now.
silly and convoluted, but it's what worked for me. i was experiencing this exact issue when i was flashing JB roms on my nexus s. i'd always assumed it was a problem with the rom.