Coding errors (or coding_exceptions) are problems that are probably caused by incorrect code. For example, a plugin that does not communicate correctly with Moodle core.
These errors are normally not caused by incorrect user input or temporary problems like the connection to the database server being down.
As with all error messages, it's a good idea to search moodle.org and the tracker to see if anyone else has reported the problem.
It's often helpful, particularly if reporting these errors, to temporarily enable debugging for your site. Doing so can help diagnose the source of the error, and aid in any potential resolution.
One user posted that sometimes, if you purge all caches the error message might disappear!
This question is of a type that is not installed on your system. No processing is possible.
This is caused because you are attempting to see/use a Quiz that uses (at least) one question that has its status as 'Draft', not ready. Change the status of the question (in the Question bank) to 'Ready' to fix this.
Block type ... has been disabled by the administrator
See the discussion Coding error detected, it must be fixed by a programmer: Block type admin has been disabled by the administrator. for a possible cause of the error plus solution.