When installing Plupload module to work with Media module on a Hostgator site, I got the error:

Your server is capable of displaying file upload progress, but does not have the required libraries. It is recommended to install the PECL uploadprogress library (preferred) or to install APC.

Looking at the suggested library (pecl.php.net) it was a shell script that pretty obviously required privileges that I would not have on a shared host. However, Hostgator has another library already installed that implements PECL: CodeGen_PECL. It just has to be enabled.