Folks do it all the time; there's no limit. Any error message? What version is in use? Reinstalling might be worth a try.
Here is the latest. For licensed users upgrades are free for up to six months. After that, VP will continue to fully function but a fee will be required in order to register the newest.
If you take a few minutes to share a project that balks at 1080 export someone will check it out. It's not difficult...
Here's how... http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material you can link it in a personal message (PM) to me, via the envelope above. Be sure to FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to share it.