Hmmmm... "all of my tables" - not sure, but that might perhaps be it, that including all your tables (perhaps forgetting primary key/foreign key fields) in one form is preventing the recordsource from being updateable. (BTW on top you say all tables, in bottom only one? I'm assuming the first line is correct)
Would using comboboxes be an option in stead of showing all table information? Could you perhaps try using main/sub forms?
To experiment, you might try recrating the form with less information, and add it incremetally, to see at which level the form get's in 'Allow additions=no' mode (and avoid those fields, if some are found)
Else, I don't know. These are just suggestions based on the information given. If this doesn't help, perhaps someone else might visit this thread.
HTH Roy-Vidar