The message above is from the following code in wp-admin/includes/file.php
if ( ( !$type || !$ext ) && !current_user_can( 'unfiltered_upload' ) )
return $upload_error_handler( $file, __( 'File type does not meet security guidelines. Try another.' ));
Which would suggest that you're using an invalid type or extension, or in other words, you've not added that type of extension or file type to the whitelist for upload media.
I was going to provide a codex link for a list of default mime types, but i can't find one, so here's the list straight from the core..
'jpg|jpeg|jpe' => 'image/jpeg',
'gif' => 'image/gif',
'png' => 'image/png',
'bmp' => 'image/bmp',
'tif|tiff' => 'image/tiff',
'ico' => 'image/x-icon',
'asf|asx|wax|wmv|wmx' => 'video/asf',
'avi' => 'video/avi',
'divx' => 'video/divx',
'flv' => 'video/x-flv',
'mov|qt' => 'video/quicktime',
'mpeg|mpg|mpe' => 'video/mpeg',
'txt|asc|c|cc|h' => 'text/plain',
'rtx' => 'text/richtext',
'css' => 'text/css',
'htm|html' => 'text/html',
'mp3|m4a' => 'audio/mpeg',
'mp4|m4v' => 'video/mp4',
'ra|ram' => 'audio/x-realaudio',
'wav' => 'audio/wav',
'ogg' => 'audio/ogg',
'mid|midi' => 'audio/midi',
'wma' => 'audio/wma',
'mka' => 'audio/x-matroska',
'mkv' => 'video/x-matroska',
'rtf' => 'application/rtf',
'js' => 'application/javascript',
'pdf' => 'application/pdf',
'doc|docx' => 'application/msword',
'pot|pps|ppt|pptx|ppam|pptm|sldm|ppsm|potm' => 'application/vnd.ms-powerpoint',
'wri' => 'application/vnd.ms-write',
'xla|xls|xlsx|xlt|xlw|xlam|xlsb|xlsm|xltm' => 'application/vnd.ms-excel',
'mdb' => 'application/vnd.ms-access',
'mpp' => 'application/vnd.ms-project',
'docm|dotm' => 'application/vnd.ms-word',
'pptx|sldx|ppsx|potx' => 'application/vnd.openxmlformats-officedocument.presentationml',
'xlsx|xltx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml',
'docx|dotx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml',
'onetoc|onetoc2|onetmp|onepkg' => 'application/onenote',
'swf' => 'application/x-shockwave-flash',
'class' => 'application/java',
'tar' => 'application/x-tar',
'zip' => 'application/zip',
'gz|gzip' => 'application/x-gzip',
'exe' => 'application/x-msdownload',
// openoffice formats
'odt' => 'application/vnd.oasis.opendocument.text',
'odp' => 'application/vnd.oasis.opendocument.presentation',
'ods' => 'application/vnd.oasis.opendocument.spreadsheet',
'odg' => 'application/vnd.oasis.opendocument.graphics',
'odc' => 'application/vnd.oasis.opendocument.chart',
'odb' => 'application/vnd.oasis.opendocument.database',
'odf' => 'application/vnd.oasis.opendocument.formula',
Which as you can see does not provide .3GP as a media type..
There are a few options, add the extension with a filter yourself, or use a mime type plugin to add any additional media types you require.
One such plugin can be found here.
http://wordpress.org/extend/plugins/pjw-mime-config/
fiddlah
