Terragen and wine - a speed comparison

I commented last week about the difference in speed between running Terragen natively in windows and using wine to run the application under linux. Here's 2 screenshots, the first shows the render output from my Vista installation,
as you'll see from the title bar the render finished in 45m55s. Here's the incomplete render in Kubuntu/wine

so that's 17 hours 57m44s (!). When I've tried before there wasn't quite this disparity between the 2 environments. Most of the time on Ubuntu was overnight - and I was asleep so it wasn't due to system busyness. I haven't used XFrog plants previously maybe this is a cause but wine claims to be of a similar performance to the native app - clearly that's not true here.