My friend has the exact same issue, and we can't seem to find anything else on the internet that even resembles the problem except this other Apple discussion thread.
She's running Safari 6.0.2 on Lion and this issue is pushing her to use other browsers because Safari loses some or all of the tabs she had open.
Almost every time she quits and reopens Safari, this issue causes a few or most of the tabs to be blank (like completely white blank) with "Search Google or enter an address" in the address bar and nothing left but the original title of the tab at the top of the window, exactly as described above. It isn't clear why only some of the tabs are usually lost, but it seems like older tabs are lost first.
Please, any suggestions would be helpful.