Problem #1 is running programs like Onyx or Cocktail. Those are meant for people who understand what they do, and what the risks of running them are. They are not some kind of shotgun panacea as so many people seem to insist in making them out to be. Programs like that can cause problems like this, and part of the problem is that if you don't really know what it is programs like Onyx do, you can spend a long time chasing down a bunch of blind alleys. I can tell you are highly unlikely to know what Onyx does because you also seem to think that repairing disk permissions is a magic cure. It, like Onyx, is just one of those things that the clueless idiots of the world have latched onto in an effort to try and feign understanding, rather than admit they're a clueless idiot. So at least you're in good company, as plenty of other people have fallen for that one. While I'm on this kick, if someone tells you to reset the PRAM to solve this issue, they're one of the clueless idiots trying to feign understanding I was talking about. Also, never, Never, NEVER listen to ANYONE who tells you to run some kind of program to control the fan speeds. Programs like smcFanControl. In fact, if you ever see anything about the SMC mentioned in a program, DO NOT RUN IT. You start messing with those settings and you can do physical damage to your computer.
Just for starters, try going into the user accounts part of system preferences, and change the way the system logs in from automatic to having to select a user and enter in a password, etc. Reboot, log in, then go back and change that setting again back to the automatic login. See how that works first, though after running a program like Onyx there's no real way of telling if you've done some permanent damage to the OS that will require a reinstall to fix.
my iMac 27'' boots to the desktop sometimes then other times it goes to the user accounts and I have to restart and then it boots to the desktop as normally does. This started after I went on vacation for 2 weeks and ever since it has this boot up problem from time to time.My osx is lion and I've run onyx and gone to utilities to check the disk permissions.Any suggestions?