User switching locks up and more

Question

I had Lion OSX on my 27" iMac. A few weeks ago the screen would just go black while you would be on the computer, just randomly. Could not wake it up to come back on. You would have to press the power button 3-4 times to get the screen back. I took it to Apple Store and they came to conclusion it was the LCD. So $560. later I came home with my computer. Started it up and new problems began. Three times it went into sleep and I tried to wake it up some hours later...it wouldn't wake up. I would have to force it down with power button then turn back on. So I took it back again to Apple Store...and of course they ran their checks and found no problem. They forced it into sleep twice and woke it right up. I don't know if it being in sleep for longer period of time at home caused it to not wake up...but in any case they found nothing wrong.  Highly recommended I upgrade to Mountain Lion, saying that would certainly run smoother and likely fix any issues.  I said I was hesitant to upgrade yet due to it just coming out...and the "Genius" said no reason at all to worry.
So went home and upgraded. Now NEW problems!
My wife and I are both users on the computer. You can no longer switch users between us. You get the box with the name and spinning wheel and that's it...locks up spinning. Have to force the computer down and rebook under the user you want to use.  Does anyone else have problems switching between users with Mountain Lion?
Plus Apple Mail constantly unexpectedly quits now.
I have been a faithful Apple user for several years...3 iMacs at my office, at home with my wife and kids we have 3 iMacs, a MacBookPro, 3 iPhones, and 3 iPads. But...all that being said I am now a VERY frustrated customer...not only in the product issues, but the so-called "Geniuses" in the store.

Answer 1

Please read this whole message before doing anything.
This procedure is a diagnostic test. It won’t solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.
Third-party system modifications are a common cause of usability problems. By a “system modification,” I mean software that affects the operation of other software — potentially for the worse. The following procedure will help identify which such modifications you've installed. Don’t be alarmed by the complexity of these instructions — they’re easy to carry out and won’t change anything on your Mac.
These steps are to be taken while booted in “normal” mode, not in safe mode. If you’re now running in safe mode, reboot as usual before continuing.
Below are instructions to enter some UNIX shell commands. The commands are harmless, but they must be entered exactly as given in order to work. If you have doubts about the safety of the procedure suggested here, search this site for other discussions in which it’s been followed without any report of ill effects.
Some of the commands will line-wrap or scroll in your browser, but each one is really just a single line, all of which must be selected. You can accomplish this easily by triple-clicking anywhere in the line. The whole line will highlight, and you can then either copy or drag it. The headings “Step 1” and so on are not part of the commands.
Note: If you have more than one user account, Step 2 must be taken as an administrator. Ordinarily that would be the user created automatically when you booted the system for the first time. The other steps should be taken as the user who has the problem, if different. Most personal Macs have only one user, and in that case this paragraph doesn’t apply.
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the page that opens.
When you launch Terminal, a text window will open with a line already in it, ending either in a dollar sign (“$”) or a percent sign (“%”). If you get the percent sign, enter “sh” and press return. You should then get a new line ending in a dollar sign.
Step 1
Copy or drag — do not type — the line below into the Terminal window, then press return:
kextstat -kl | awk '!/com\.apple/{printf "%s %s\n", $6, $7}'
Post the lines of output (if any) that appear below what you just entered (the text, please, not a screenshot.) You can omit the final line ending in “$”.
Step 2
Repeat with this line:
sudo launchctl list | sed 1d | awk '!/0x|com\.(apple|openssh|vix)|edu\.mit|org\.(amavis|apache|cups|isc|ntp|postfix|x)/{print $3}'
This time, you'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. You don't need to post the warning.
Note: If you don’t have a login password, you’ll need to set one before taking this step. If that’s not possible, skip to the next step.
Step 3
launchctl list | sed 1d | awk '!/0x|com\.apple|edu\.mit|org\.(x|openbsd)/{print $3}'
Step 4
ls -1A /e*/mach* {,/}L*/{Ad,Compon,Ex,Fram,In,Keyb,La,Mail/Bu,P*P,Priv,Qu,Scripti,Servi,Spo,Sta}* L*/Fonts 2> /dev/null
Important: If you formerly synchronized with a MobileMe account, your me.com email address may appear in the output of the above command. If so, anonymize it before posting.
Step 5
osascript -e 'tell application "System Events" to get name of every login item' 2> /dev/null
Remember, steps 1-5 are all drag-and-drop or copy-and-paste, whichever you prefer — no typing, except your password. Also remember to post the output.
You can then quit Terminal.