Android 4.0 isn't available for the Droid Incredible.
Prehaps you are trying to load the Gingerbread update.
Does your phone have enough memory free space to install the update. There are several other posts with steps to take to free up the memory and allow the update to complete.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
I have the same issue. My Incredible said it wanted to download a 4.0.... update and did not have enough space. I freed up space and it downloaded. It says is is ready to installed and counts down to reboot then nothing happens. This has happened repeatedly. Any thoughts?