Hello,
For me it's fixed !
I would say that 1.6.0.11 is not the problem. For me was ovverides and modified tables in the DB ...
Then once I understood that I did not go into details and made a fresh install. Then copying datas from the tables I wanted to keep (products, transport,cms,delivery,orders,customers ...).
SO, i'm not giving solution here, but fresh install works just fine for me. Check your modifications if they are 1.6.0.11 compatible and also your DB.
Then this does not mean that there's no problem with update ? But at least I have a 1.6.0.11 working with my previous data.
In case you choose this way don't forget to keep your old settings.inc for password encryption purpose.
(sorry for poor english, I'm french )