Arduino Mega 2560 not uploading sketches/working

My Arduino Mega 2560 are not working any more. I unplugged and plugged every thing back in. I tried to upload the blink sketch but all I get is a timeout error. The LED is constantly on and the TX and RX are not on. I have read that it could be the boot loader. How can I fix this problem? Have a project that needs to be done by next weekend.

This happened to me where it uploaded a couple times and then stopped after I tried doing things with serial. Now I got it working again by pressing the reset button when it finished compiling. I know this doens't work for all boards though.

Dante12129: This happened to me where it uploaded a couple times and then stopped after I tried doing things with serial. Now I got it working again by pressing the reset button when it finished compiling. I know this doens't work for all boards though.

Is there a migration guide from Arduino pre 1.0 to Arduino 1.0?

When I had tried compiling an old sketch on Arduino 1.0, there were compile errors. I didn't want to deal with them, so I went back to 0023.

At some point- once I'm ready I'd like to move over to 1.0.

Is there a list of things that one must to work with the new compiler?

thanks