I got the same error when submitting to SQL Server. I don't know exactly why, but what fixed this was changing my DSN source from the newer "SQL Server Native Client" to one just using the plain "SQL Server" driver.
I haven't seen really any SQL Server/Infopath tutorials, though youtube seems to have the most Infopath tutorials in general. For a very basic intro into setting up SQL Server on Infopath, check out this one (based on the Infopath beta):
DB Journal
Please let me know if come across any other helpful tutorials.