Question : Workflow Foundation 4 (WF4) or SharePoint 2007 based on WF3?

I am about to embark on a somewhat new project.  I will be creating workflow solutions for standard supply chain-related business processes.  This will mainly be focused around MOSS 2007.  We have recently upgraded to SharePoint 2007 (sad, I know), and WF4 was released a few months ago.  I'm trying to gauge which framework is the best to begin learning.  

I have heard great things about WF4, but that it is a significant departure from WF3.  SharePoint 2007 (and 2010 for that matter) are based on WF3, so using WF4 is out of the question for MOSS solutions.  So, here are my questions that I would love some expert feedback from those with experience with these technologies.

1. I have to expand my C# knowledge to either WF3 or WF4.  Given that they seem to be significantly different, which should I learn?  Given that the main goal is working with MOSS 2007, I assume that WF3 is going to be essential.  Comments?

2. How fundamentally different are WF3 and WF4 going to be?  Is it a waste of time to learn WF3 when WF4 is significantly better and the future?

Thanks!

Mark

Answer : Workflow Foundation 4 (WF4) or SharePoint 2007 based on WF3?

This is probably a dredded corrupt Outlook profile. Have you tried re-creating your Outlook profile from the mail applet in the control panel?