Help needed with pfSense and HughesNet Satlink

I'm trying to setup a pfSense firewall with HughesNet Satellite internet service. Later on, I intend to balance that connection with a 3G external antenna to improve internet speeds and data allowance (Sat is expensive) in a remote location. But thats not really the problem.

I cannot get pfSense to serve internet from the HughesNet HT1200 modem. I can ping every IP I attempt, with the usual 600ms round trip. But there is no way to make DNS work. I've tried many workarounds, including using the DNS provided by Hughes.

I believe there is something to do with the web acceleration feature in the modem, but I cannot disable that (I tried).

Basically, every time I cycle power to the modem, I get at most 5 minutes of good internet before DNS stops. Then I can only access sites with addresses cached by Safari. That is also affecting every other device on the network, including the firewall. I even tried to disable all packet filtering, to no avail.

Another interesting thing is that the modem doesn't even load the web accelerator configuration webpage after DNS stops working. And even when it does, unchecking the option that should disable it has no effect. Upon refreshing, it's still enabled, and there is no "save" button.

Can anyone shed some light? Without pfSense the internet is working, and pfSense is working with other connections.