You can also test your model to make sure the integrity of model is OK.
Backup your converted model and enable expert mode (Settings | Options, section General, checkbox Expert mode). Open the converted model, right click its model name in Physical Model Explorer or Application view and select Test model and see the the results in Message Explorer.
If there are no errors, could you send us previous error log with Access violation? The default location on WinXp is C:\Documents and Settings\USER_NAME\Application Data\Quest Software\Toad Data Modeler\TDM.elf.
If there are some error messages (double-click the message will display the details of failed test) you can try to repair it (right click the model name and select Repair model). Then run the test again. If it doesn’t help, let us know or please send the model to firstname.lastname@example.org. You can try to test/repair your (backuped) logical model before conversion too.