In order to get Oracle support PHP was compiled with --enable-sigchild option. When PHP is compiled with --enable-sigchild, proc_close() [return codes are broken]. SquirrelSpell uses the proc_open() and proc_close() functions to run spellcheck, if PHP 4.3.0 or newer version is detected. The plugin depends on correct proc_close() return code.
You can force use of older spellcheck code by editing plugins/squirrelspell/modules/check_me.mod.
Find
if( check_php_version ( 4, 3 ) ) {
and bump up the PHP version, for example to
if( check_php_version ( 5, 3 ) ) {
Future SquirrelSpell plugin versions will have option that allows to select used spellcheck code, but it might be unavailable in 1.4.x plugin versions due to big number of changes made in plugin.