There are still a number of bugs with version 1.48.66. The one in particular that’s been slowing down your render is the issue with transparency. Any materials with an alpha transparency layer (in your case, the leaves on the trees) slow down the render drastically.
The ASGVis crew is working on a patch to fix this and several other problems the new version has been having. No date has been given for the release of the patch, but hopefully it’ll be sooner than later.