This may be a bit technical for some, sorry for that:

On the DoMove page, when you submit the move you are making on a game, the submit button is before the combobox and a few other input values. One of those inputs is the game ID (g).
On a slow connection, because of the combobox options, the submit button is sometimes visible before the end of the form. When I'm on a really slow connection (which luckily doesn't happen often) impacient as I am, I click the submit button when it shows, before the rest of the form has been sent to my browser. In this situation I get sent back to the main page and no move is made. I then have to reload the whole board and do my move once again.
I'm not sure if the option in the combobox is absolutely necessary for the move to be submited but I'd say that the game id definitelly is ;)

So could the hidden input with the game id be placed before the submit button? Maybe this nasty side effect would go away...