Suddenly cannot change the calendar for an event in iCal?

Question

When I creart new events, they now automatically are asigned to the top calendar group (as listed on the left side of the iCal screen).  When I try to edit the event and asign it to a different calendar, the menu only shows the calendar groups, all in grey, not the individual calendars. 
When I go to preferences to investigate what's going on, I only see the calendar groups, all in grey, not the individual calendars.
When I click on the "+" sign in the top-left corner, same problem, only the calendar groups appear, all in grey.
Why can I suddenly not access these calendars when editing an event?  Why do they stop showing up in the editing menus? 
The calendar still show up in the list menu on the left. I still can add new calendars and new calendars groups.  The problem occurs when I try to assign an event to a specific different calendar.

Answer 1

Saw your post Beth over on my thread but I thought I would respond on this one since we're all here.
Hi y'all (^_^)
Sorry to meet under such horrid circumstances, but it's nice to know that I'm not the only one.
I've found out a few things that didn't work so here's the list to save you both some heartache.
No type of re-install fixes is. Not a partial reinstall of the OS where you keep your data or a full wipe.
Checking your permissions or scanning the disk for errors doesn't work either. Creating a dummy user account to see if the problem ports over is a waist of time. If you don't have free support on your machine don't spend money on opening a ticket.
The problem is specific to the Mountain Lion release 10.8.3. The only fix that I have found while I wait on apple is to regress back to 10.8.1 (18.8.2 has the issue also) . . . reverting isn't hard to do with this nifty program I found but nearly impossible for me as I purchased my iMac in February of this year and the firmware came with 10.8.3 in the recovery partition. I've been scowering the net looking for anyone with a 10.8.1 full install dmg (not the update) but everyone either thinks I'm pirating software or doing something impossible so needless to say I'm still running 10.8.3
But all is not as bad off as we think. The problem is only with Calendar (or contacts, whichever place originated the problem as I have found the majority of people on the net who have encountered this did so while in the Contacts program not Calendar). This is a good thing! Because since the problem is unique to the software of origin (Calendar for us) that means we can still use use Calendar and the cross-program functions of Calendar (like creating an even from mail or inviting someone from your contacts) as if nothing is wrong. All programs that read event or calendar files work just great, only Calendar is having the issue. In other words, keep using Calendar like there isn't a problem.
This is a hard pill for me to swallow because I see that there is still a problem and I am itching to fix it. My obsession is only causing me to drink. I have tested this theory by creating a whole new schematic on iCal where I have 6 new Calendar groups all with at least 3 calendars in it and multiple events. (I'm a small business so they're not just dummy events). The great news is everything works like it should as long as I take precautions.
Here are those precautions:
1 - When creating a new event MAKE SURE YOU ARE IN THE CALENDAR YOU WANT THAT EVEN TO BE IN since you won't be able to use the drop down and choose later because it is greyed out for us.
2 - If you run into this loop where you can't save changes to an event (happened to me a few times when the problem first materilized) just pop the calendar that even is inside to the base calendar list. In other words, take the calendar out of the group, make your changes, then click and drag it back into the group. Even if the event is recurring everything will be fine. Groups only alter the hierarchy of how iCal stores and displays the files, not the files themselves which is why other programs aren't having a problem reading them.
After I made my slew of new groups I tried a few things out to make sure everything was actually still working and it all came out perfect. You can still publish, sync to google, or iPhone, or android and things will display just as you expect them too. Reminders even worked. The problem is ONLY inside iCal and even then only when trying to use that drop down menu.
Long story short, if you can deal with knowing in your gut that things are f.u.b.a.r but keep going about using iCal as if it isn't, then you will survive the long wait (prob 2-3 weeks) until the 10.8.4 patch comes out or worse yet the 10.8.5 major release this summer.
Sorry this is such a long post (and for the misspellings) but sharing is caring so let's get through this together. Plus I don't know about y'all, but I spent 3K on my iMac so if this b!tch ain't gonna work like it's suppose to then it better be because of something major. . . I figured you all might be feeling the same so I should tell you just how major this bug is. And it is major, so much so that people are literally creating programs to disenfiect 10.8.3 out of their machine. If the application developer working with me comes up with a fix I will update the thread. Until then, try not to pull you hair out (~_~)