What build of Expression Media 2 are you on? That is, what's in parentheses in the version number. If it's 2092 you have an outdated build and should install 2096, but auto update would not detect it because they are both SP2. If you need to install 2096, you can find it at
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=bb6aa4e5-1101-4116-9513-030679a14b77. 2092 used a two stage rendering process that we discovered some major problems with after release. That's why 2096 was developed.
If that's not the case, I'm not at all sure what the problem is. However, in practical situations, does the delay cause you any trouble, really? How fast to you need to arrow through the images in Light Table?
Regards,
Anita Oakley