the modem you purchased has a built in firewall, you need to set it to allow ICMP ping. if you already have then AT&T is blocking the ICMP protocol, there excuse will be for security measures.
Well, the problem has been solved. Both modems are working fine (I'm using the D-Link though for obvious reasons). The problem was that they were not attached to a filter. Now please before everyone calls me a noob, AT&T told me to do this. I originally had it connected to the filter when I set it up originally, but then the DSL line would not connect, so I called them and they told me to do that. It worked for a while and I had the correct speeds until a few weeks ago. Anyway, it's all running nicely, and thanks to all those who helped!
