Anything that I copy on my desktop gets deleted automatically after a few seconds. Any idea what is going on ?

Question

I have a problem with my MBP.
One day something weird started happening. Every time I would copy / save / download something on my desktop it got deleted automatically after a few seconds. On very very rare occasions this would not happen.
This has been going on for 3 months now and I haven't found any sollution. The last option is to format and reinstall Lion but I hope there is a faster/better solution than that.
I have a 2011 15-inch MBP with the up-to-date Mac OS X Lion.

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 four lines of text in monospaced type, which are UNIX shell commands. They’re harmless, but they must be entered exactly as given in order to work. If you have doubts about the safety of running these commands, search this site for other discussions in which they’ve been used without any report of ill effects.
Some of the commands will line-wrap in your browser, but each one is really just a single long 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.
To begin, launch the Terminal application; e.g., by entering the first few letters of its name in a Spotlight search. 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/ { print $6 $7 } '
Post the lines of output (if any) that appear below what you just entered (the text, please, not a screenshot.)
Step 2
Repeat with this line:
sudo launchctl list | sed 1d | awk ' !/0x|apple|com\.vix|edu\.|org\./ { 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.
Step 3
launchctl list | sed 1d | awk ' !/0x|apple|edu\.|org\./ { print $3 } '
Step 4
ls -1A {,/}Library/{Ad,Compon,Ex,Fram,In,La,Mail/Bu,P*P,Priv,Qu,Scripti,Servi,Sta}* 2> /dev/null
Important: If you synchronize with a MobileMe account, your me.com email address may appear in the output of the above command. If so, change it to something like “[email protected]” before posting.
Remember, steps 1-4 are all drag-and-drop or copy-and-paste, whichever you prefer -- no typing, except your password.
You can then quit Terminal.