Ok, so im a noob to all this stuff, but hear me out. I have an optimus s that has worked great until today. The 3g wont come on at all. The icon doesn't even show. I can only think of two things that might be the cause.
1) I switched to a different phone (a rumor, I believe) for a week so I wouldn't have to bring my nice phone camping. Maybe changing to a non smartphone changed the settings? I just switched back today and noticed the problem.