Janice, do you have this problem with our plugin only or with any plugin you are trying to upload through the Admin Area? If the problem occurs with our plugin only, please try to download the plugin archive from the Store and upload it once again. If this doesn't help, please PM your admin and cPanel access details and we will check into this issue.
In case the problem occurs with any plugin/theme, this means that the problem is with your server settings. Please check out these topics: https://www.google.com/...;espv=2&ie=UTF-8