Error trying to compile dhtmlxscheduler.css in rails project

I’m trying to asset compile the dhtmlxscheduler.css file in a rails project but it doesn’t like the string !ie which occurs twice in this file. I’m not familiar with this syntax and so I’m not familiar with what I need to modify to get it to compile. For now I’m just removing it and I don’t notice any difference. Any suggestions? Here is the error:

Invalid CSS after “…n:-4px 0 0 -4px”: expected “;”, was “!ie;}div.dhx_fo…”
(in acme/vendor/assets/stylesheets/dhtmlxscheduler.css)

Technically css allows custom “!text” for the styles, browser will just ignore unknown rules.
The “!ie” placed there to define IE specific styles, check recurring form in IE7|8 - position of radio and checkboxes will be shifted a bit.