Odd Rendertimes

Hi!

I am workin on a little shortfilm as a kind of first bigger project to improve my skills. But now I discovered a really strange problem. One File has really high rendertimes per frame. The times I have to wait going up to nearly one hour. This is really strange because I rendered a month ago a testimage with a slightly higher vertexcount, the same objects and the same Rendersettings and materials. The only bigger difference is that I rendered it in the half resolution. There the rendertime were about 12min on my laptop with Blender 2.49b.

Firstly I thought that maybe the higher resolution is the problem but also the renderpreview ist really, really slow. Maybe someone here can help me to solve this problem. I uploaded the file here: http://www.pasteall.org/blend/1069

And here my laptop specifications:

Ubuntu 9.10
Acer Aspire 5920G
GeForce 8600m GT
2GB DDR2 RAM
Intel Core2 Duo T7300 2GHz

I tried to render the file now with the Blender 2.5 svn Build (r24444) and got an amazing rendertime from 46 seconds. But this doesn’t help me at all. I don’t dare to work with a developementbuild.

I heard about rendertime problems in the 2.49b release for linux. Is this the problem or could it be something else?