We've had other problem reports like this and found that most were caused
by the WDEF virus or a corrupt System.
To eliminate the WDEF virus as the cause, follow the instructions in the
Tech Info Library article titled "WDEF" Virus: Information.
If the problem persists:
1) Remove all items from the System Folder that you want to save, like
third-party INITs, CDEVs, and DAs.
2) Trash the System Folder.
3) Reinstall the system software from locked, known-good disks.