Today I suddenly was afflicted by the "crash on launch" problem that I have seen other complain about. I also stumbled across a solution that worked for me, but of course YMMV. It exploits a "trick" I learned a while back when using NSCA Mosiac on Solaris -- and had no idea it would work in OS X until I started poking around....
Here is an abbreviated list of the steps that restored Chimera to its old (new?) self: (Yes, you will have to use the Terminal. Sorry!)
- From your home directory, type cd .mozilla/Profile/Chimera
- Find the funny-named directory that ends in '.slt' and cd into it.
- Type ls -laF and look for a file named lock@. It is a symblic link.
- Remove the file it is pointing to. In my case, I typed rm 127.0.0.1:373.
- Restart Chimera and enjoy!
Again, I cannot promise this will work for everyone, but it worked for me twice now, whereas reinstalling older or newer versions of Chimera (including from the nightly build) did not.