bug when choosing different variants of product

[Spoh]

Hi,

 

I have a problem in my store with my variants when I want to choose e.g. a different size or color.

 

Here's an URL: http://jkofficeline.dk/85-bordplade-med-centerbue.html#

 

Its a table top and when I want to choose the dimension: 200 x 100 cm it doesnt stay with that option. It goes to the lowest option instead. Though the second time I click 200 x 100 cm it stays on there BUT if then afterwards I choose another parameter, like another color etc. It changes again.

 

Does anyone know how to fix this bug? (its a problem both on my theme and on default.)

 

Thanks