ctrl key problem

I am using vine server 3.11 on OS X 10.6.2 and connecting via RealVNC personal edition 5.4.3 on windows XP.

Everything is working well apart from one very annoying thing:
I cannot use Ctrl + key combinations.

As you can imagine, this makes interacting with the remote command line tricky.
I have used the OS X on screen keyboard viewer and the ctrl key press is recognised, but I think that the additional key then gets registered as a second event (evident by showing up as a character in the terminal)

I have tried every combination of keyboard event source to no avail. Other modifiers work fine, eg: command-tab, shift etc.

Help!

If all else fails, you can use the “do” line at the bottom of your Eggplant “Last Run” window.

Enter: TypeText controlKey, “a”
Result: highlight all

Enter: controlKey, altKey, deleteKey
Result: opens the Windows security dialogue