RESOLUTION 1:
Reset the Toad user files. Here are the steps:
NOTE: If some of your folders / directories are hidden, open a Windows Explorer window | go to Tools Menu | Folder Options | View Tab | click “Show hidden files and folders” | click Apply | then click OK.
1) Fully Exit Toad
2) Go to:
C:\Users\(username)\AppData\Roaming\Quest Software\Toad for Oracle
3) Rename the folder that is named with the version of Toad you are using. For example, if you are using v13.3, then rename the '13.3' folder to '13.3 Old'.
4) Start Toad and test the issue to see if it is resolved.
If the issue is not resolved...
1) Close Toad.
2) Go to C:\Users\(username)\AppData\Roaming\Quest Software
3) Rename the "Toad for Oracle" folder to "Toad for Oracle OLD”
4) Start Toad and test the issue to see if it is resolved.
Note: If you would like to get your saved connections and settings back, take the following steps.
1) Close Toad.
2) Copy the connections.xml and Toad.ini files from one of the following folders, depending on which steps above you had to take to resolve the issue.
C:\Users\(username)\AppData\Roaming\Quest Software\x.x Old\User Files (where x.x is the version of Toad you are using)
C:\Users\(username)\AppData\Roaming\Quest Software Old\User Files
3) Paste the files in the C:\Users\(username)\AppData\Roaming\Quest Software\x.x\User Files folder.
4) Launch Toad and see check to make sure your connections and settings are back. If one of these files was what was causing the problem, then the issue may come back.
RESOLUTION 2:
Use the 64-bit version of Toad for Oracle, instead of the 32-bit version.
STATUS:
Waiting for a fix to be released in a future version of Toad for Oracle.