upgrade from 2.7.1 to 2.8 error message

Tried to upgrade to 2,8 automatically but times our like other posts here.
so did it manually via plugin upload.

Now have error message appearing top of page at site and admin.

Warning: include_once(/home/bow13936/public_html/DevWP/wp-content/plugins/wordpress/) [function.include-once]: failed to open stream: No such file or directory in /home/bow13936/public_html/DevWP/wp-settings.php on line 473

Warning: include_once() [function.include]: Failed opening ‘/home/bow13936/public_html/DevWP/wp-content/plugins/wordpress/’ for inclusion (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/bow13936/public_html/DevWP/wp-settings.php on line 473

Site still works though.

Any thought anyone please. I’m new to all this. Was the pugin upload the right place to install this upgrade? Was that my error.