Did you create them in 7.30? Are you reloading the project or just a subtitle file?
Or are subtitle positions - top/middle/bottom/etc. not being saved? If that's the case, be sure to Apply Format To SELECTED SUBTITLES, under the Format tab.
If this doesn't solve the issue, please post images. Here's how...
http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/