Possible suggestions:
• turn off anti-virus protection
• check to see that all "enable synchronization" check boxes and so forth are checked. Microsoft put in some weird redundancy.
• choose appropriate settings in drop down menu AND Settings button. Microsoft has weird ways of organizing stuff.
• If you have already run the conduit once, I believe you then have to check the boxes labeled "Do once and then syncronize". Again, Microsoft's methodology is ridiculous.
If it still doesn't work,
check this e2sync thread.
This is a third party conduit that runs as a whole seperate deal. It will even sync your Treo 650 categories with Entourage categories and iCal calendars and vice versa. Same for Address Book and Tasks.