I have an issue with Spark working on Windows 7 under Domain User account (non admin privilages). User can log on but spark works slow and user cannot see what is typing and other posts in room. I tried on same computer with admin account and everything works ok. Also gave full permision on foder where is spark instaled and same issue.
Try deleting his profile and start with a fresh profile.
Yes, it woks. I delete spark folder (from app data / roaming ) and start spark ap again and it now works fine.