Inadvertent configuration change

I have been using wireless with Linux boxes for several years. Used a 
Prism card on an old Dell laptop running RH7.2 (that gives an idea of 
how long I've been at it). And now on an HP pavilion with Fedora Core 4.

Up until recently, I had no problems getting access through APs all over 
the world (literally), but recently I think I may have made an 
inadvertent change somewhere and cannot figure out what I have done.

When I access an AP, I find that I must determine the AP's gateway and 
manually add it in using the /sbin/route command. I never used to have 
to do that, and it is a nuisance.

Any ideas what I may have done? Directions where to look?

Thanks.

Bill Lee