Multi-DB: Blog 1 Shows Blank Page

I was using Multi-DB plugin 2.9 for WordPress MU 2.9.2

Recently upgraded to WordPress 3.0.1 and Multi-DB 3.0.2.

The main blog displays blank page with no errors.

I have enabled WP_DEBUG in wp_config.php but still no errors or warnings appear. The PHP log does not display any errors either (though it normally would). All I get is a blank screen + blank error log.

I have also temporarily removed all of the other MU plug-ins that could be interfering.

I am able to access ALL of the 3000 other blogs and the wp-admin perfectly fine.

The root blog (i.e. blog_id 1) was previously located in the database wpmu_c4 (because MD5(1) = c4...) with table prefix wp_1_

Now that I am on WordPress 3, it seems that Multi-DB expects my main blog tables to be located in wpmu_global (i.e. the global database) with table prefix wp_ so I have moved those tables to comply.

I get the feeling that the code must be hitting a dumb exit(); instruction somewhere.

Please help me diagnose this problem!