When using autofire, and then switching to autoattack, you get the messages autofire off attack on. However, even though you stay in combat mode, you don't actually attack. You have to either hit autofire again and then melee attack, or hit melee attack twice to actually start meleeing.
This was on my frog rogue using the summoned fangs and ragebringer. This is with the Titanium client. I haven't verified if this bug exists with the Faydwer client.
EDIT: I just verified this bug exists with the Faydwer client as well.