Finally figured out a decent workaround for getting past the reservations not showing up once one logs into hyatt.com.
Workaround:
1) Close browser.
2) Throw computer in the trash. (kidding)
3) Click on the "change reservation" link in any of the current emails from hyatt.
This appears to log one in correctly and refresh whatever cookies are causing the website to not work as intended. Sadly, I've had to do this like 3-4x this morning booking reservations... but at least gets one moving along.