I have some include()d functions that calls pg_connect() and pg_close(). If I call two functions (two different or two times the same), any pg_xxxx() at the second function will generate the "Warning: is not a valid PostgreSQL link resource xxxx". Or, if I call one of these functions with some pg_connect() at the main code, this second pg_connect() will generate the warning too.
This SAME CODE runs without problems in 4.0.2
My configure command for 4.0.3pl1 (the same I used with 4.0.2) was: './configure' '--with-apxs=/usr/local/apache/bin/apxs' '--with-config-file-path=/usr/local/apache/conf' '--enable-versioning' '--with-mysql=/usr/local/mysql' '--with-pgsql=/usr/local/pgsql' '--enable-ftp' '--with-gd=../gd1.3' '--enable-bcmath=yes' '--disable-debug' '--enable-memory-limit=yes' '--enable-track-vars' 
I have tested with the standard php.ini file.