I went to Database | Export | Export DDL. I ran through the steps and when I click on 'Export object DDL' I get the error:
"Access violation at address 01390E77 in module 'toad.exe.' Read of address 0000002C."
A know cause to this issue is choosing to export all constraints beginning with 'SYS_.'
Example of "SYS" prefixed constraints:
Do partial DDL export with constraints beginning with 'SYS_.' It not clear how many you can select at once. You may want to try braking up the DDL export into three or four parts.
Waiting for fix in a future release of Toad for Oracle.