config file

having a slight problem with a config file. have an enterpise solution. there are 6 different projects in the solution. at the begining of the program the user can change the location of the database that they want to connect to. the change is then stored in the config file. my problem is that the changes to the config file are not coming through until the app is stopped and restarted. i am not sure why if i stop the code after the change and then look in the bin dir at the config file i can see the change reflected in the file. when i step through to the database layer the connection string is built from the config file but it seems to be the old version and values and not the version that has had the changes in it. all the dll share the same bin dir and so are there with the config file. i must have some setting wrong but not sure what. please any ideas!!!! keith