plugin error

1) Can’t install new plugins- error message:

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/dobie516/public_html/megabirthdaysite.com/wp-admin/includes/class-wp-upgrader.php on line 186

Incompatible Archive.

Plugin install failed.

2) can’t open theme-editor.php. error message:

OOPs, no such file exists! Double check the name and try again, merci

I can work in the Appearance: Widgets and Menus.
I can create pages and such.
I can add Media and Links
The existing plug-ins are working, they were installed before this error occurred.
The theme-editor.php is on the CPanel server.

website: https://www.megabirthdaysite.com

Thank you for looking at this.