Try a few things. Try to power down your modem (the one your ISP gave you) and then your router.. Power your modem up, wait for the right lights to come on, then power up your router (basically a power cycle). I find that helps more often than not.
Try also clearing your cache, and if you have the game installed try uninstalling and re-installing.
I would check out the GHOSTS SUPPORT forum as well. Or Message ATVIAssist here or on Twitter for more help.
Good luck, hope you are able to get on soon.