Please perform these steps:
Go to
C:\Users\<username>\AppData\Roaming\Quest Software\Toad Data Point 5.3\
and rename it to
C:\Users\<username>\AppData\Roaming\Quest Software\Toad Data Point 5.3 - old\
Go to
C:\Users\<username>\AppData\Local\Quest Software\Toad Data Point 5.3\Cache
and delete all content there.