User Synch fails claiming url or key problems

Im setting up an WPMU only site (all your tehemes and plugins etc... and then migrating my other site to it step by step and trying out your features),

So far, so good. If this works, I have a partner and ALL their sites should be converted to this.

I wanted to import my 36 tester users, and cannot get this to work. I have tried the following:

1. Master site
2. Sub site (both these sites are on the same host Arvixe but separate accounts)

I have tried switching the sub and the master, and it claimed it succeeeded.

I then switched back, and deactivated all plugins except user synch on the master.

Then from the Sub site, no luck. From the Master Site it says it DID synch, but nothing actually came across.

I tried multiple variations and combinations with no luck.