when i click on the "play online at ubi.com" icon and then enter my username and password I get the error message "the client is incompatible with the server". So how do I get to play online?

Online play for Chessmaster 9000 doesn't work anymore.

This is clearly stated in the Chessmaster 10th Edition FAQ... please take time to read it before posting questions.

i have the same problem,but if i log in without playing the games its ok?

It sounds like you're confusing the normal login with playing online... the only part of Chessmaster 9000 that won't work any longer is Online Play.