I upgraded our site from 6.1.4 to 7.0.3 using the following path(each executed individually):
--6.1.5--6.2.0--6.2.1--6.2.2--6.2.3--6.2.4--6.2.5--7.0.0--7.0.1--7.0.2--7.0.3

There was an error in the sqlprovider on the first upgrade, but I saw that was for the blog module we don't use anymore. Our site initially was still using the iconbar, so I went into the host settings to switch it to the controlbar. I couldn't select anythign from the dropdownlist. I was slightly incuriated and manually switched it to the controlbar in the database only to find that nothing would drop down when I hovered over edit, or any of the other options, so i switched in the database to the ribbon bar. All was well, except When adding a module, the DROPLIST wouldn't work. Hmmmm....

Sure enough, NONE of the droplists on the site would work. I also noticed that there were a few javascript errors sure enough.

--Uncaught TypeError: Property '0' of object is not a function Telerik.Web.UI.WebResource.axd:6

--Uncaught TypeError: Object #