Whenever I try to run DCT on the 8.5.1 client I get a message to restart my Notes client

Had the same problem, took the easy way out.

 

Erase it completely.   (both the template and the database)

 

Download the template fresh from here:

 

http://www-01.ibm.com/support/docview.wss?uid=swg24019358&rs=0&cs=utf-8&context=SWA00&dc%C3%9400&q1=dct

 

Create a new db with the template

And don't bother with the check for updates (It has bad date-time, and will always say it has one to offer)