I found a bug with the input_asset_tag in Firefox 3 - It is unable to locate the form name using "this.previousSibling.previousSibling.form.name" in sfMediaLibraryHelper.php.
A simple solution is to add the following code to sfMediaLibraryHelper.php after:
$form_name = 'this.previousSibling.previousSibling.form.name';
Add:
if (isset($optionsform_name?))
{
$form_name = '\.$optionsform_name?.'\;
unset($optionsform_name?);
}
Then when you call input_asset_tag() you can add the form name to the options variable:
input_asset_tag('somename',,array('form_name'=>'MyForm?');