Thanks, sjgadsby, but I have a slightly different symptom - not a connection error, but rather Maemo's "Select connection" dialog (the one with the list of access points) appears.

Also, regarding your bug, have you tried restarting your tablet after disabling the "Update Automatically" checkbox? I discovered in my testing that I had to restart the device after removing Modest in order to actually stop the "Select connection" dialog from appearing and draining my battery. I think the modest daemon may continue to run in the background even after uninstalling modest (until a restart).

(Obviously, having to restart the tablet is not ideal, but it may help the developers to know if restarting helps.)