iPhone 3G Loses Functionality With iOS 4.0

Update 2: Thanks commenters - power cycling the iPhone 3G resolved the issue.

Update: Lifehacker has instructions for returning to iPhone 3.x

I was on my iPhone 3G last night and pressed the home button to look at my calendar, and nothing happened. Prior to "up"grading to iOS 4.0, I could always be on the phone and read my email or calendar or surf the web to look something up. With iOS 4.0, I can't. 

I would like to go back to iPhone OS 3.0. 

Comments

[James Katt]

Can you clarify the issue?

in iOS 4, double-clicking the home button was repurposed to access apps that are being multitasked.

in iOS 3.x, double-clicking the home button can be assigned to Home, Search, Phone Favorites, Camera, or iPod.

In either iOS 4 or iOS 3.x, when in a phone call, pressing the Home button takes you to the home screen where you can select another app to run while in the phone call - such as Calendar or Safari or Mail, etc.

Perhaps you have to do a hardware restart on your iPhone if you can't do this.

[Fred]

Have you set up the home button actions under general settings?

[Jeff]

I'll try these things and see if the behavior changes.