pgAdmin III does not appear to handle passwords with spaces in them.
Leading and trailing spaces simply fail to authenticate.
Internal spaces produce the error message: missing '=' after 'xxx' in connection info string
Where 'xxx' is the part of the password after the space.
For reference, I'm using pgAdmin III 1.0.2 on Win2k against PostgreSQL
7.4.1 on sparc-sun-solaris2.9, compiled by GCC gcc (GCC) 3.3
-- "The blues are multicolored." -- Dave Lambert
Daniel Risacher magnus@alum.mit.edu