Currently my Mango update for Windows Phone fails with error code 80004005.
Answer from Microsoft:
“This is an error that is still being diagnosed at Microsoft. At this time there is no workaround for it. You should restore your phone to its NODO image and wait until there is a resolution for this problem.”
Some suggestions from Microsoft
On these crash / update issues there are two general approaches that you can try.
1. Try to apply the update using a different desktop / laptop system.
2. If a different system still doesnt' help, then remove any personal data from the device and perform a hard reset. Then try the update process again