Updating beyond WordPress 4.2.1 yields “allowed memory size exhausted”

Edit line 149 in file.php as described in this thread:
https://wordpress.org/support/topic/unable-to-update-plugins-after-upgrade-to-42

fixed it for me (on a linux host).

edit: just read you are on windows: someone also posted a fix that applies to windows hosts there (apparently more complicated because backslashes are used in filepaths).

so your line 149 in file.php should read:

if ( empty( $filename ) || '.' == $filename || DIRECTORY_SEPARATOR == $filename ) {

good luck 🙂