Yes, theme my login would solve this problem, but opens a new one: even it is translated to german the text displayed on my (german) website is mixed english/german. i tried this plugin some days ago and settled with "login with ajax" and a handmade design of the login/register/password lost pages.
now this is slowly driving me crazy on worpdress/jigoshop: when solving one problem, a new one will be created. and this register/logon/lost password stuff is handled very badly by wordpress & jigoshop *grim*
anyway, using another plugin is the only possible solution you say? to bad...