1998 passport alarm

The factory keyless entry on my 98 passport has stopped working. The ironic thing is that last week I replaced the batteries in my remote and it worked great for a couple of days. Then one morning the car did not react to my remote.

I am going to do the re-programming instructions found in the FAQ when I get off work later today, but are there any other possible causes that anyone has run into? Is it normal for this to have to be done with a remote that was already paired with the vehicle? I haven't tested the batteries but I find it hard to believe that they would last less than a week, even if my pocket depressed the buttons constantly.

if you replaced the batteries and did not reprogram the things there is no possible way it will work they must be reprogrammed after battery relacment