error message in admin when plugin activated

I would like to use your plugin on a WP multisite install.
Whether I use “network activate”, or I activate on a specific site, as soon as I activate, all my admin pages are displayed with the following error message, displayed 3 times :
array_flip(): Can only flip STRING and INTEGER values! in C:\inetpub\wordpressMUtests\wp-admin\includes\menu.php on line 274
Please notice I use a plugin developed by myself which customize how menus are displayed. But it works fine will all the other plugins I use. It is only when I activate your plugin that I get this error message.
Please advise.