Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
The color of your PC?
What did you change?
What is the exact error-message, does it happen at every location and with every plane (also the default planes and at locations with no add-on scenery installed)?
If it happens everywhere and with every airplane, it's something global. Do you load programs with FSX? Have you tried a new driver?