Error Code -50 on different internal HDDs

Question

Hello Community,
I got a really exotic problem. After month of usage without any problems, my system  (Mac OS X 10.8.2, MacBook Pro (Mid 2009), 500GB Hitachi HDD build in afterwards) failed its service multiple times out of a sudden.
Symptoms:
- System freezes after few tens of minutes after reboot (while working)
- previous attempts of saving/dublicating/pasting of files failed (message like "This process could not be finished, because an unknown error has occured. (error -50)")
- Download, install and opening of Apps wasn't possible anymore (propably because of writing errors, too)
- After restart (often only possible with hard-boot) sometimes troubles with access rights (key chain access denied etc.)
- Mail, Calendar, Messages were forgetting their accounts (and could remember afterwards sometimes)
- and just by the way, my battery life decreased from 5h to 2h hours with the nice notice "check battery"
I know, some of you are already thinking "Completely clear, dying HDD.", but the best is still coming
Counter-measures:
- Clean install of Max OS X ML + migration assistent => same problems
- Repair of rights and volumes with disk util (sometimes started from recovery partition or from Install-USB-Stick; checking done multiple times, also directly after freeze+reboot) => rights-repair could be done without problems, volume check without anz problems, S.M.A.R.T. Status is "verified" (or "checked" if translated by word)
- Clean install without migration of Apps and configs (only data) => same problems
- EXCHANGE of intern HDD by old intern HDD (until then, it was used as extern one without any troubles) + clean install von Mac OS X ML without migration of anything (only single data imported manually) => SAME PROBLEMS AGAIN, Disk util checkings without any problems again (beside some standard Java confusions)
Sometimes, after a clean install, I created a new admin account and deleted the old one, but this shouldn't be the reason for such big troubles which appear repeatly.
I have not even a clue, what the reason could be. Did someone has had such problems once knowing a solution? Every tip would be great.
Greetings, Mario.

Answer 1

Back up all data now.
This procedure will unlock all your user files (not system files) and reset their ownership and access-control lists to the default. If you've set special values for those attributes on any of your files, they will be reverted. In that case, either stop here, or be prepared to recreate the settings if necessary. If none of this is meaningful to you, you don't need to worry about it.
Step 1
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 icon grid.
Drag or copy — do not type — the following line into the Terminal window, then press return:
sudo chflags -R nouchg,nouappnd ~ $TMPDIR.. ; sudo chown -R $UID:20 ~ $_ ; chmod -R -N ~ $_ 2> /dev/null
Be sure to select the whole line by triple-clicking anywhere in it. You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. You don't need to post the warning. If you don’t have a login password, you’ll need to set one before you can run the command.
The command will take a noticeable amount of time to run. Wait for a new line ending in a dollar sign (“$”) to appear, then quit Terminal.
Step 2
Boot into Recovery by holding down the key combination command-R at startup. Release the keys when you see a gray screen with a spinning dial.
When the OS X Utilities screen appears, select Utilities ▹ Terminal from the menu bar. A text window opens.
In the Terminal window, type this:
resetpassword
That's one word with no spaces. Then press return. A Reset Password window opens. You’re not going to reset a password.
Select your boot volume ("Macintosh HD," unless you gave it a different name) if not already selected.
Select your username from the menu labeled Select the user account if not already selected.
Under Reset Home Directory Permissions and ACLs, click the Reset button.
Select  ▹ Restart from the menu bar.