If Eclipse with installed Perforce (P4) plugin hangs on start trying to load a workspace and in WORKSPACE/.metadata/.log you see something like this repeating again and again:
============
!ENTRY com.perforce.team.core 4 0 2013-07-12 17:17:31.375
!MESSAGE Perforce password (P4PASSWD) invalid or unset.
============
This simple action may help - just remove if exists ".p4tickets".
On Linux:
rm ~/.p4tickets
On Windows:
del C:\Documents and Settings\<username>\p4tickets.txt
Solution was found here: http://osdir.com/ml/version-control.perforce/2005-12/msg00125.html
