I cant find anything out about your specific card, its not even listed on the Creatix site on either the German or the English one, although the German one did cover a few more products than the English one did.
I have looked on a few forums that came up during a search for your card but most were in French or in German and no one seems to have your specific problem, from what I could read of them, although the main problem seemed to be getting a connection at all, not disconnecting after a few minutes.
I would look in the Power Save Mode and makes sure thats disabled or set to user control or something like that as it may be disconnecting to save power after a set duration.
Other than that I cant really offer any more as I havent used a wi fi card myself