open phpbb_config (phpBB_ is the table prefix: change if yours is different
filed cookie_domain: change the value to
.frogmen.info (note the leading dot)
clear /cache (leaving index.htm and .htaccess in place)
Clear browser cache
If you deleted the extension files, put them all back.
Then try again.
If that doesn't let you access the board: I suggest you restore your working 328 version and re-update AFTER disabling extensions.
Extensions which are incompatible with phpBB3.3 should be disabled, data deleted and only then files removed.
We should embrace problems, without which there wouldn't be any solutions.