Note: This MIME detection issue applies to Easy File Uploader 0.6+ module and also to Easy Flash Uploader 0.3+ plugin.
There is a known issue with version 0.6 of the module and some hosted sites. This was introduced after hackers used the 0.5 version of my module to hack someone's site. As a result I added extra security that detected the actual MIME type of the file. Version 0.6 works great with sites that have PHP 5.3 or higher, because the fileinfo functions are available in those versions. However, for sites that use PHP 5.2.x or lower, the module will only work if the server allows the calling of the PHP function exec. To check for this, in Joomla 1.5, go to Help -> System Info -> PHP Information, and search for the value of the "disable_functions" directive. If exec is listed in this list, and you are using a PHP version below 5.3, then MIME detection may not work for you. If you want to check what may work, please download my short test script, and place it in your hosting site, and then access it. For example: http://www.michaelgilkes.com/test_script.php
I really do NOT recommend the use of any version below 0.6, because of the security issue that occurred. If you have PHP 5.2.x or lower and the exec function has been disabled, I recommend that you talk to your hosting provider to allow you to enable access to exec (typically) by removing it from the "disable_functions" directive in our php.ini file. Most hosting providers are willing to help its clients. Also, from my understanding it can be done by setting up a custom php.ini file for your account.
Hope this helps someone. I regret if the new releases inconveniences some folks, but I can't allow a repeat of the hacking incident. So, I encourage everyone to uprade your module, as well as your PHP version, asap.