Can't VNC to machine after changing name

[Int]

Here's my setup, simplified for explanation:

3 computers. The first is named CPU1, second CPU2, third CPU3. They need to be re-ordered in relation to their physical location. So, for example, they are lined up like so:

CPU2 CPU6 CPU7

and need to be

CPU1 CPU2 CPU3.

Note, this is for explanation purposes, not real life. So, we decide to re-name the machines, and rejoin them to the domain (after clearing their old references from the domain of course - all of that is done by the book). So we rename CPU2 to CPU1, and CPU6 to CPU2, CPU7 to CPU3.

Now, if I VNC into CPU1, it works, but in the VNC window shows the machine name as CPU2 instead. You can also access this machine by VNCing to CPU2. So the new CPU2, which was CPU6? It's invisible. I can't get to it because VNC is pointing to the wrong machine.

Does anyone know why this is, or if there is a relatively easy solution for it? It seems to be an AD issue, but I'm not sure.

[redge]

dns resolver problem of ultravnc,
you should use ip instead

ipconfig /flushdns
ipconfig /registerdns