1. At startup the game loads all resources into temporary browser files, this is shown by the progress bar on the start screen. If you have the game loaded quickly then everything is normal.
2. When the game is loaded at the start of each layout, all layout objects are loaded into video memory. If you have a long loaded layout may be you layout takes too much video memory or other problems in the layout itself.
To understand more precisely you need to look at the problem.