If your connection isn't encrypted, you may want to check out what's going on with your IP distribution. Potentially resetting your gateway completely and changing your security type may resolve the issue.
I would call Comcast, maybe it's something in their settings or they know the solution. Your wife cant be the only one of their customer to have this problem. I didn't even know that Comcast was an Apple authorized cellular iphone provider company (and if they are not, that could be the problem).