WordPress MU

I have set WPMU to use separate domains, so not sure if that could be the problem, but....when trying to upload files from one of the blogs I get the error:

"Warning: Invalid argument supplied for foreach() in /wp-includes/functions.php on line 1122"

"File type does not meet security guidelines. Try another."

Line 1122 of functions.php is:

foreach ($mimes as $ext_preg => $mime_match) {
$ext_preg = '!\.(' . $ext_preg . ')$!i';
if ( preg_match($ext_preg, $filename, $ext_matches) ) {
$type = $mime_match;
$ext = $ext_matches[1];
break;
}
}

Any help would be greatly appreciated,
Brandon

I have the same error uploading a file for my theme.
I also have more than 1 domain.
I used the plugin "MultiSiteManager".

When I look to the code you gave, it means that "$mimes" is not a array.
I looked more deep in the code :
usually this part of code (wp_check_filetype function) is called without the "$mimes" argument, and the default value has the "jpg" extension I tested.
The only way this "mimes" could not be an array, is from the wp-admin/includes/file.php

line 139 : if ( $test_type ) {
		$wp_filetype = wp_check_filetype( $file['name'], $mimes );

I did not go further.
What should I do ?
directly modify this line 140, deleting the "$mime" ?

I resolved my problem quite simply :
just validate the "site-admin=>options" where the list of allowed file-types has to be set.
the default is already proposed, but it seems that it is not set in the database... so just validing the form is enough.
(that's what I think, I didn't make all needed research to prove that)