guilhaume's dashboard

Hello, I have a dell studio 1537 latop since 1 month. I had not problems with charging, but now I have one. When I plug in, the adapter is recognised but not charging, and I have the following error message:
"THE AC POWER ADAPTER CANNOT BE DETERMINED, YOUR SYSTEM WILL OPERATE SLOWER AND THE BATTERY WILL NOT CHARGE. PLEASE CONNECT A DELL 90W AC ADAPTER OR HIGHER FOR BEST SYSTEM OPERATION".
Some people have the same problem http://en.community.dell.com/forums/p..., but I don't find any answer... Can you help me please?