Denford Software & Machines

Hi there , i'm very new to this cnc so please bare with me .
I have a conect 250 cnc router date of manufacture is 1998 , when i try to put it into machine mode i get this code

Access violation at address 005BA3BA in module windmill.exe. Read of address 0000000

The software is denford v 2.29
The machine is a large bench top type with a ally cabinet around it e stop button and so on .

Like i say i'm very green so to speak so any help at all will be great , thanks Andy

First thing is to double check the dongle rights as mentioned in another reply.
Then check you have the correct machine selected in VR milling - if not:
Choose menu Setup > Setup machine parameters > password: denny
Then right-click on CONECT250 on the tree view on the left, then choose Set As Active machine.
Whilst in parameters, also check that the ComPort under the communications section is correct - ie is the machine plugged into COM port #1 or #2 etc..