Vista - rdp can't connect

Hi

I have 2 computers A and B running vista.

From computer A I can connect without any problem to computer B.

This morning I changed the motherboard of computer B.
I did not re-install vista on computer B, only new drivers. Everything works
as before on computer B.

But now i can't anymore connect from computer A to computer B.
I got an error telling me that the certificate is no more valid.

I tried to save a .rdp file with option to connect anyway if
authentification failed.
I tried to reboot.
I deleted one certificate in crtmgr.
Nothing never changed, always the same message.

I tried to connect to computer B from an other computer C with windows XP on
it and it works fine.

My last solution is to re-install vista on my computer A. that's weird.

Does anyone have an other solution ?

Thx.

I've just downloaded KB907077 from windows update.

Things are working now.