I have them same problem, I am running a new install, and I am having various errors in WordPress uner MySql 5.0.15. From what I Can see MySql 5.x is much more strict in terms of how it enforces tabel restaraints and default values, ie it won’t insert if the sql does not account for all required fields, and no default was given.
I am still digging to see if I can throw MySql back to not enforcing these rules at this level.