Toad does not remember passwords after logging into a database.
Make sure the save passwords option is enabled. You can find this option on the bottom left corner of the connections window.
1. Close Toad.
2. If in a version of Toad prior to 9.7, navigate to the C:\Program Files\Quest Software\Toad for Oracle\User Files directory. If in version 9.7 or after navigate to the C:\Documents and Settings\<Profile_Name>\Application Data\Quest Software\Toad for Oracle\9.7\User Files directory.
3. Find and rename the connectionpwds.ini file to connectionpwds.old,
4. Re-launch Toad.
The connectionpwds.ini file is where your passwords are all saved. Doing the steps above will create a new connectionpwds.ini file.