who has locked my account?

if you have to identify on which windows client / server a given account is currently logged on sysinternals utility "psloggedon" is your friend.

a simple "psloggedon account" identifies all computers the given account is currently logged on (and part of the same domain you start this command).

this tool is part of sysinternals huge amount of useful tools and command line helpers which helps to answer or identify common maintenance issues, like

• does my application doesn't close all used handles
  Process Explorer
  
• which resources (filesystem, registry, ...) does my application access
  Process Monitor
  
• capture of debug output (traces using OutputDebugString, DbgPrint) without using a debugger
  DebugView
  
• .....

and all utilities are free. the team creating and maintaining those utilities are now part of Microsoft. up to now this has any negative effect to utilities they provide beside there is no source code available anymore which prevents to see how certain information can be / must be retrieved to be on the safe side.