I believe there were some yet to be announced enhancements to the calendar and signup system.
What you might be seeing may not be an error but may be related to the change.
The little button next to the month and year is one. If you mouse over it you should get a clickable mouse pointer. This now takes you to a full calendar view page.
edit:
It looks like the color for an event is now exclusively controlled by the Category. To change this under admin you would need to go to Event Categories and either edit or create a category for each type of raid/instance.
--
Six Demon BagJack Burton: Hey, what more can a guy ask for?
Egg Shen: Oh, a six-demon bag!
Jack Burton: Terrific, a six-demon bag. Sensational. What's in it, Egg?
Egg Shen: Wind, fire, all that kind of thing!