InfoPath Dev

How do I resolve this error? 

Also, how do I check the log?

I've read some posts about secondary connection causing this error but I do not have 2 connections. The 'Show Error Details' has the following message:

An unexpected error has occurred. The form was not saved.
The submit event handler returned a value indicating that the submit failed.

What is the form doing when submitted? Just a regular data connection to submit to a SharePoint Library?

In ShP 2010 - on the server, the log files are generally: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\LOGS\

In ShP 2007 - on the server, the log files are generally: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\LOGS\