Toad: Table Autocomplete Functionality Not Working

I've been using Toad for more than a year now without problems. All of a sudden the table autocomplete feature has ceased working. No settings have been changed, and I've clean installed a new TOAD version, yet the problem persists.

The image below shows autocomplete defaulting into view IN_INSTRUMENT in schema MCDM. Normal behaviour should result in a table/view list.

It is notable that the above does not happen with all schemas. For some schemas I will still see a table list. In the beginning this error happened only with a single schema. Now it is slowly progressing to other schemas as well, which is exceptionally frustrtating when you're dealing with dozens of schemas that contain hundreds of tables each. It slows down development when you must open Schema Browser and look for the exact table/view/procedure/package each time instead of letting autocomplete give suggestions.

This same issue has been described in this thread and and this thread with less detail, yet no accepted answer has been given.

As can be seen from Code Assist settings, these should be in order.

How to reset autocomplete behaviour into what is its original state?

I've found the solution to this problem. The issue was a corrupt configuration file. For anyone else with the same problem, this is how I fixed mine:

1. Backup your appdata folder - you can find its location in options -> general -> application data.

2. Create a new set of user files using Utilities -> Copy User Settings -> Create clean set of user files. Make sure you are running Toad with administrator rights.

Note that the above will delete all your saved connection details (schema names, passwords, connection strings), so take a note of these.

Hope this helps someone in the future.