Hmmm.. couple of more things I would try.
Have you done anything to the online.tmpl file?
It's odd that it's just you. That extra info it seems to be showing you is the code that represents what the person is looking at etc...
Try the query (or us PHPMYAdmin) to delete all the data from the w3t_Online table. It'll get filled in again automaticaly.
DELETE FROM w3t_Online
Then you could try this SQL Query:
REPAIR TABLE w3t_Online
See if that fixes anything.
Beyond that, I'm stumped. You might need a trouble ticket so that infopop can look at your files and DB.
