Currently Being ModeratedJan 10, 2013 3:37 PM (in response to scrapbooker59)
Delete the account. Restart the phone by holding the HOME and SLEEP buttons at the same time until an Apple logo appears (about 10 seconds). Then add the account back.
Currently Being ModeratedJan 10, 2013 4:54 PM (in response to Lawrence Finch)
I tried this. After setting up a new account and clicking next, it told me to log onto yahoo.com! Still not fixed. Says Yahoo server unavailable, the same thing it's been saying for 3 days.