Are you using the latest webix 3.3 ?
There was an error in IE, similar to the reported one, it was fixed by updating the font file
Also, please try to use webix.css from our CDN ( http://cdn.webix.com/edge/webix.css ), it will use fonts from CDN as well. If error will not occur for CDN files, it means you have incorrect headers for font files, while serving them by a local web server.