Images upload – error message

Uploading images gives the following error message:

“Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘media_admin_css’ was given in C:\wamp\www\sieino.mine.nu\wordpress\wp-includes\plugin.php on line 339“
I have the plugins: Flexible upload v1.13, Change Uploaded File Permissions 3.1 and Lightbox 2 v2.0.2 installed – among others.
WP v2.7.
What is the solution to get it to work correctly, I wonder now. . . .

Eno