Local Internet Connection - Little or No Connectivity

my problem goes like this, and maybe one of you guys can help me. i have a dell inspirion 1150, thats about a year old. i have service pack two and all of that and for a wireless i dont have the dell default i got a us robotics wireless reciever. ok my problem is this, most of the time when i log on to a network i get the little or no connectivity message after waiting for about a minute while it says that the connection is aquiring a network ip address. this is mostly smaller networks, like starbucks or personal wireless (home) networks. funny thiing is that it has done this also with the hard line connection (dsl cable etc) so its not like the problem is limited to wireless . but like right now im in an airport and it has worked fine, and also at my school i can use both wireless and ethernet. im not sure if it is because of the size of the network or what the problem could be. i called the dell help line but they didnt know what the problem was either. they suggested a forum. so i think thats about it. most of the time when not on my schools network ( which always works ) it doesnt aqquire an ip address i guess. i dont know though. non of my settings are wrong, ive looked at the options and told it to set up an automatic ip address and everything. so yeah . . . thats it.