I'm not sure whether this has been caught...but using
MySQL 5.0.x
PHP 5.x
IIS 6.0
I tried to log in and received the error...
[nativecode=1364 ** Field 'preferences' doesn't have a default value]
PHP Error in [path]rc\program\include\main.inc (584): Failed to create new user
I changed the "preferences" field in the "users" table to allow nulls, and I was able to log in OK. I don't know whether I fouled up something else, however.
--Brent