When I place an item in the Trash, a message appears stating that the item cannot be left in the Trash and needs to be deleted immediately.

If your date gets reset to an invalid year such as 1904, this may occur under Mac OS 8.0 or Mac OS 8.1. This is more common on PowerBook models, where if the unit is left without power for a lengthy period of time the backup battery can drain causing PRAM to get reset along with the date and time.

To resolve this, open the Date & Time control panel and set the correct date.