I found an interesting gotcha with Sharepoint and InfoPath yesterday. A user called me about an error they were receiving when submitting a web-enabled form. The error was "An error occurred while the form was being submitted". It's a pretty generic error, so I started searching.
My form calls a web service, userprofileservice, to gather the user name and department from AD. When the form is submitted, it automatically titles the file, "Selected Year + UserName", i.e. "2009 John Doe". In the case of this user, his name was "John Doe, Jr." What I found was Sharepoint does not allow a period "." at the end of a file name within a list or document library. In fact, there are several invalid characters. So, I changed the automatic naming to "Selected Year + UserName + 'Plan'", i.e. "2009 John Doe, Jr. Plan". This worked perfectly and the form submits.
Thanks to this blog for helping with the solutions: http://blogs.officezealot.com/legault/archive/2007/04/26/20302.aspx