If you are running on 10G and you get "ORA-00257 ORA-16020 Archiver Stuck" then you should look at the size of your flashback-area and increase it. Most of the documentation you find about this errors is about, that the disk is full, but nobody mentioned, that there is a new feature called "flashback" in 10G and that this area also can be full.

Resize the flashback-area with for example:

alter system set db_recovery_file_dest_size = 4000000000;