Problem upgrading from 7.4.3 to 7.6.3


I just upgraded to 7.6.3 version. Everything is working fine BUT I have a big problem : the modules show a blank screen (or HTTP 500 in IE). For example, I click on an account, everyting is ok, but when I click on the menu on “Accounts” : White screen.

Sugarlog empty.

Checked my permisssions and seems to be ok …

Do anyone have a solution ? Thanks a lot in advance !

And when I enable Ajax I have : There was an error processing your request, please try again at a later time.