When I try to debug a procedure with the lightning bolt icon and clicking yes to compile dependencies I am getting two error messages on separate runs
Probe: Timeout occurred
Background session could not connect to Oracle
Running older Oracle client (8i) have been know to cause the issue.
If you are running an Oracle 8 or 8i client against a 9i, 10g, or 11g, database, try using a client that matches the server you are connecting to.
1. Go to View | Toad Options | Debugger
2. Increase the value for Debug session time out or set it to zero to turn it off