I think I figured it out - I had created another database named 'slash_backup' and had populated it with a previous dump of my 'slash' database by calling:
mysql slash_dump < slash-backup.sql
Well, I don't know mysql well enough, but I can only assume that my submissions started to be added to the 'slash_dump' database since everything seems to be working fine again, now that I deleted it.
I know, I know, sometimes I'm just too clever for my own good :-)
If I run into any more trouble, I'll alert the media again.
P.S.: If any of your have any idea what exactly was happening here, please let me know.