You don't have them in the correct order in your form. These are in the correct order, but I'm not sure how it will look without using a table or some sort of css.
HTML Code:
<span>Log In:</span>
<input type="text" class="bginput" name="vb_login_username" id="navbar_username" size="10" accesskey="u" tabindex="101" value="$vbphrase[username]" onfocus="if (this.value == '$vbphrase[username]') this.value = '';" />
<input type="password" class="bginput" name="vb_login_password" id="navbar_password" size="10" tabindex="102" />
<input type="image" src="images/styles/bgear/style/button_go.gif" value="" tabindex="104" title="$vbphrase[enter_username_to_login_or_register]" accesskey="s" />