You have hit one of the problems that all 'photoshoppers' have - what you see on the computer screen is not what you see in print or TV.
The only way is to do a test DVD, use rewriteables for testing - they save you money in the long run, and play it on your TV to see what you get.
Depending on the monitor/graphics card you are using you may be able to adjust its settings to match the camera.
Added 03/09:
Or - you have the camcorder screen set to high brightness for outdoors and the camera is underexposing so on the camcorder screen everything will look OK - the two virtually cancel each other out.
How to calibrate your computer monitor without investing money on TV monitor:
1) Play on your computer a dvd that you like the color as example one of your DVD or something created for kids as usual colr and brigthness is good.
2)Adjust the computer screen brightness
3) Run Magix with the video you need to correct, save it on a new name just to test
4) Select different part as testing purpose, aplied on each part a different brigthness may be the firat part is 10% the next part or section is 15% and as you want.
5) Burn a DVD.
Check on your TV
This open the road to color correction or white balance using the software but generally is fast and easy just to play with brightness.
If for any reason your captured video or you shot video are too dark you can adjust the brightness using the brightness function. Form menu Effets, Video effetx, Brightness Contrast.