Call them up and let them trouble shoot the problem with you. If they can't fix it then tell them you might as well cancel the account you can't afford a new box. They might offer you a free 4100 or credit to buy a new 4100. That's what happened to me a few years back.
It may not be the card that is the problem. It may be the tuner in the receiver.
You may need a new unit.
I know it's not the card that is the problem. But if I use my other 3100 from storage I will need a new Smartcard. I'm sure it's the tuner because for weeks I would get full signal and then lose the signal and the weather was nice out. Plus the 5900 was working fine in the living room.
The 3100's have been known to have the centre lead tear off the circuit board inside the units, which is a quick and easy repair.
To test for this without opening the up the unit, while connected to your TV and satellite dish, and in the signal strength meter window of the menu, place a small amount of pressure upwards with your fingers on the coax going into the receiver from the satellite dish. The upwards pressure pushes the centre lead down inside the unit, onto the circuit board, if you get signal when doing this, (and it doesn't take much pressure), it can be fixed with a re-solder job.
Check your signal strength on Transponers 05,13, and 21 ensure they are above 75%, if it isn't the signal is currently to blame (Can't recall where the guide is stored as per transponder) also go to menu 6 1 3 and ensure that you do not have any warnings present in terms of LNB Drift (Highly Unlikely but possible)
Also try doing check switch with Menu 6 1 1 and selecting check switch and then let the receiver finish it, once it is complete exit all the menus and let it come back by itself (Progress for signal) and see if it fixes itself
i have an old 3100 i got a new 6131 so i deactivated my 3100 and gave it to my son inlaw to hook up on his account . when i hooked it up it has no signal strength but his other does any one know why .its got 100 percent signal strength at my house