I haven't heard of any issues, nor had any issues myself, with the actual installation of the plug-in. I wonder if there is a firewall issue or a conflict with another plug-in. I don't have a WP site running the older versions to check, but have been using the plug-in since the older versions.
Without and extra information, I'm not sure we would be able to troubleshoot the problem. Would the dev company be able to test in on a newer version to see if they are having the same issues?