LOCK SYMBOL ON SCREEN WONT COME OFF...

SOURCE: Frozen screen, nano 2 gb

press and hold both the menu and select (middle) buttons for around 10 sec until the apple logo appears... similar to ctrl-alt-del

SOURCE: black and white screen and not recognized.

try this page
http://www.fixya.com/support/r561901-ipod_problems_start_5_solutions

note in the end of my post there is the online service assistant where you can check your warranty and setup repairs with apple if required.

SOURCE: ipod has a lock symbol and screen appears to be frozen

Nano ipod has pass code that I don't rember how do I override this to open the nano?

SOURCE: IPOD NANO 8MG HAS LOCK ON SCREEN

to unlock plug it into original computer...if thats not enough open itunes.
If it is still asking for code and you can't remember it try this:(I got this from John on here and it worked for me)- with ipod still plugged in...
Go to My computer- click on tools - folder options - then the VIEW tab - tick the box for 'show hidden files and folders' - click OK -
now click on ipod (in my computer) a light file called Ipod control double click- then Device double click - then _locked file right click and delete - disconnect ipod from computer.
this should have taken the code screen away and you're at main menu. you can reset your code.... but sometimes you need to re-boot your ipod.
You can do that by flicking the hold switch over and back...then holding in the middle button and menu together until the Apple logo appears and release.
NONE OF THESE ACTIONS ERASE YOUR STORED INFO.

SOURCE: itouch screen is white then, when restored goes black.

make sure u hold down home and sleep buttom for more than 11 seconds. After the allple logo shows up, press the home button...i had similiar problems as some of u, and this unfroze/ fixed my issue. Hopefully, it will work for u