Remote Desktop Connection Problems

Our users have used Windows Remote Desktop to connect to their computers in the office from home.  Comcast is our primary internet provider.  We had no problems for many years until last week.  Some users are suddenly unable to connect to the office.  The error that the remote machine is unavailable, may be turned off, remote may not be enabled, etc. comes up immediately, they never get to the point of entering passwords.  All the users with this problem have Comcast as their home internet provider.  I do not have Comcast at home and I am able to log on to these machines, as the users, from home.  Another problem is the people who have wireless home networks have found their iphones will not send or receive email from our Exchange server while they are in their house.  As soon as they leave, it starts working.  I've had one of them try using a firm laptop to connect, to see if it was something with their home computer, and the laptop could not connect either.  I had them try connecting directly to the cable modem to bypass the wireless router and that didn't work so I know it's not their wireless setup. We have called residential support and they claim nothing has changed on the Comcast side.  Well, something has changed and residential support doesn't know about it.  I really need to get this resolved.  We're a law firm and this is effecting about 8 attorneys.  If anybody has suggestions or if anybody can get me in contact with somebody at Comcast who could check this out, I'd be forever thankful.