Just a quick note as I’ve seen other people hit this. There are a couple of reasons that can cause an OVA deployment to fail when using the Web Client on vSphere 5.5. Two solutions are here and here. But if that’s not it you may also want to check your DNS.
In my home lab I often don’t use the lab DNS on my RetinaBook and iMac all the time and that causes the issue for me. When you deploy the OVA the client wants to talk directly to the vSphere hosts and tries to resolve the host names. If it can’t it’ll throw this error which isn’t very descriptive or helpful. So either hardcode it in your hosts file or make sure and point to a DNS server that can resolve the names.