Unable to remove login items

Unable to remove login items (Revert after reboot) iOX10.5 iMac
I am having issues and permanent encounter in having my removed login items reappearing after reboot. I have very MANY of the same programs in 'open at Login accounts' eg: Messenger,Safari,Skype,Evernote,Dropbox,antivirus, but they are listed dozens of times. in this 'open at login' area.

Here's the steps I have taken:
1) Open Setting, Account Preferences, Click a program, click the -delete
2) Remove some login items (with or without unlocking the lock, doesn't seem make a difference, tried both)
3) Login items are now fewer
4) Reboot
5) voila, the removed login items are still loaded and displayed in login item tab.

How does one solve this? Tried to google, but....

Login or startup items which are found in System Preferences, Accounts, Login Items, is just one place where programs can start up from. You should go there first and remove all the login items you don't want. Unlock the lock, remove the login items and then close the lock.

However, if a program is starting up from elsewhere, it will continue to startup each time you boot or reboot.

You say:"if a program is starting up from elsewhere, it will continue to startup each time you boot or reboot."
How will I know if this is the reason for my problem? Is there some way for me to check? Also, I do unlock the lock and try to delete all the login items. I'd expect them to disappear instantly, but it takes about 4 minutes for 6 items to disappear. And I have 100's. Dozens of the same names, but only some of them 'checked'. I'm baffled.

If you have as you say, hundreds of startup items listed, then I suggest a reinstall of OS X. Something is very wrong with either your account or the system.

I will re-install the OSX and see if this makes any difference. Thanks for your time.