Hello, migration to iCloud is impossible because updating iPhone 3GS from v 3.1.2 to v 5.0 fails

Hello,

Here is my configuration

iPhone 3 GS 16 Go, iOS v 3.1.2

Airbook Mac OS X v10.6.8

MobileMe account since 2009

(all in French)

Here is the problem

I am trying to migrate from MobileMe to iCloud. Several trials to update the iPhone with iTunes to v5 however failed. Safeguarding iPhone content takes > 6 hours and blocks at about 10 %. Syncing iPhone and Mac is no problem. Thank you very much in advance for your help.

Best

Agricola Lepre