In the version query-ui-1.8 the dialog buttons lose the styles.

When you open a dialog,the buttons within the dialog pane lose the styles except the hover styles. To solve this problem you need to change the method in the file jquery.ui.dialog.js where the dialog are created. In the next lines it will be shown the lines of the new method corrected.

_createButtons: function(buttons) {
		var self = this,
			hasButtons = false,
			uiDialogButtonPane = $('<div></div>')
				.addClass(
					'ui-dialog-buttonpane ' +
					'ui-widget-content ' +
					'ui-helper-clearfix'
				);

		// if we already have a button pane, remove it
		this.uiDialog.find('.ui-dialog-buttonpane').remove();

		(typeof buttons == 'object' && buttons !== null &&
			$.each(buttons, function() { return !(hasButtons = true); }));
		if (hasButtons) {
			$.each(buttons, function(name, fn) {
				$('<button type="button"></button>')
					.addClass(
						'ui-state-default ' +
						'ui-corner-all'
					)
					.text(name)
					.click(function() { fn.apply(self.element[0], arguments); })
					.hover(
						function() {
							$(this).addClass('ui-state-hover');
						},
						function() {
							$(this).removeClass('ui-state-hover');
						}
					)
					.focus(function() {
						$(this).addClass('ui-state-focus');
					})
					.blur(function() {
						$(this).removeClass('ui-state-focus');
					})
					.appendTo(uiDialogButtonPane);
			});
			uiDialogButtonPane.appendTo(this.uiDialog);
		}
	}