image upload problems

[francis1tree]

Hi I am trying to do a really simple task - upload an image into a Page! But every time I try this I get an 'HTTP Error' and a window appears saying:
'Error 500 - Internal server error
An internal server error has occured!
Please try again later.'

I have tried both the browser upload and Flash loader
The image jpg file size is only 96Kb.
Site is http://www.scalemodelling-now.com
Image file name is kinetic-f-16i-israeli-sufa-storm-1.48.jpg

(I had problems yetserday with using NextGen Gallery which could not be resolved and was told there might be an issue with 1&1 my hosting company and PHP memory allocation?)

Surely I can upload an image??!!
Any ideas VERY gratefully received, thanks.
Francis