Can you try out the solutions mentioned in this thread? (http://forums.adobe.com/message/2911542)
Some of the solutions are:
- Disable real time scanning on your anti-virus software.
Enusre that you have the latest version of graphic drivers for your computer installed. For example, if you are using a Nvidia driver, verify that it is the latest by checking out their website.
Welcome to the forum.
I would start with this ARTICLE, which begins with a checklist on things to get PrE working best, then goes into some tuneup tips for the computer and OS, and finally lists links on troubleshooting, including the one that Preran linked to above, where more information is requested.
Good luck, and let us know how it goes.