Same error (Error SQL DB function failed with error number 1060) upgrading a 1.7.3 multilingual site (En, Nl, Fr) to 2.5.0
Multilingual site is constructed following the new Joomla guidelines.
Fixing the database fixed the errors but NOT the site (some 404's)
After restoring (thanks Akeeba!) second try by first removing the en-GB content language as suggested elsewhere in this thread. Result: a blank site page.
Got everything finally fixed.
As mentioned elsewhere, deleting cache everywhere you can is important and also checking the versions of installed extra modules and plugins.
On one site however, a stubborn problem was only solved after switching to another front-end and admin template and then going back (problem was: clicking the options icon in article manager did NOT open the params in a pop up but in the article manager page itself, causing that page to hang whenever you wanted to save or quit, so you had to 'manually' go back. I suspect it was still a problem with some cache somewhere.
Nevertheless, hats off for the developers