I solved my problem following these steps
1. Delete cookies related to Apple in Safari
2. Delete the Genius.itdb
3. Sign out of iTunes Match
4. Rebooted and turned on Genius
5. After Genius is done indexing, I turned on iTunes Match - I got an error saying 'iTunes Match is synchronizing with another library - do you want to proceed?'. I clicked Yes
6. iTunes Match started indexing and within 20 minutes it was done (I have 20K songs in my library).
This morning, I encountered the same error again (could not reach server). Delete the Apple cookies in Safari, got the iTunes Match error (synching with other library), clicked Yes and within 5 minutes, iTunes Match was ready to go.
Somehow I think this is related to info in the Apple.com cookies. Let me know if this works for you too.