2 NICS - bridging network - controller PC

I have a networked PC with 2 NICs.
One is connected to our business network, with a static IP address (10.38.75.xx) the other NIC (10.42.10.xx) is connected to a Controller machine.
The business side of things works fine - network access & internet access works well.
The intent with this PC is for a vendor to be able to RDP it (which he can) then open a browser and use the Controller's IP address (10.42.10.33) to access and control the connected machine.

I am an administrator - logged in as myself, and trying to browse to this IP address, the page tries to load forever. It never times out or displays an error - just continues trying to load.

At first, the vendor that was accessing this machine, when logged in as himself, COULD get the web page to open up at that IP - but he wasn't authorized to install an activeX program that needed to be installed. Logged in as myself, I couldn't get to the point where it asked to install the program.

Because I couldn't figure out how to fix this, I just set him as a local administrator as a short term fix - now he can't access the web page either. I've tried setting him back (removing his adminstrator privileges) - but now neither of us are able to access this page.

Any suggestions??
Amber

 

Which network is he RDP'ing in on?

 

He's RDP'ing on the business network - connects to the PC fine - but he is unable to connnect to the Controller via a web browser.

 

I'm gonna go old school and say reboot everything. That usually fixes it.
Does the controller respond to ping?

 

It seems a reboot of the controller itself has fixed the problem.
Thanks for you help.
Amber