There is the same question listed under http://stackoverflow.com/questions/427007/the-key-userid-does-not-exist-in-the-appsettings-configuration-section, but unfortunately none of the answers worked in my case. All was working fine, I checked everything in and when I opened the solution again, it started crashing on the above. I cannot find any hint of what I am doing wrong. Any ideas?

<?xml version="1.0" encoding="utf-8" ?> 
<configuration> 
    <appSettings> 
        <add key="URI" value="http://123.123.123.123:8080/smsxml/collector" /> 
        <add key="Provider" value="123" /> 
        <add key="LongCode" value="+123" /> 
        <add key="PassWord" value="123" /> 
    </appSettings> 
</configuration>