Might be a cache and or cookies issue...
From your Safari menu bar click Safari > Empty Cache
Now go back to the menu bar again click Safari > Preferences then select the Privacy tab.
Click Details. Type yahoo in the search field top right corner of that window then click Remove All > Done.
Quit then relaunch Safari to test.
If that didn't help, back to the Privacy tab. Click: Remove All Website Data
See if that helped.
Ok.. try this.
Go to ~/Library/Caches/com.apple.Safari/Cache.db
Move the Cache.db file to the trash.
Restart your Mac, launch Safari.
And try disabling the Lion "resume" feature...
Open System Preferences > General
Deselect: Restore windows when quitting and re-opening apps
Quit, relaunch Safari to test.