I keep getting an error message about afcads for airports I have updated.
And the message is ?
I want to rebuild the scenery data from scratch again.
You can try removing the C:\ProgramData\Microsoft\FSX\SceneryIndexes folder, this will force a complete rebuild. But, if one of your AFCADs has a problem, this won't fix it, that's why I've asked the exact error message.
Also, it might be helpful having a look at your Couatl.LOG file, from the GSX Troubleshooting section.