A client logged a problem which I needed to look at through the GP 2010 client, so I logged onto their server and ran up GP.
Or at least I attempted to. After double clicking the Desktop shortcut I received the following error message;

Fortunately, knowing the clients system fairly well (I did their last two upgrades) I knew the dictionary was located on a shared network drive accessed via the UNC path. I checked and found that the user account I had logged on with did not have access to this location.
A quick log out and back in under the admin account and I was able to open Microsoft Dynamics GP 2010 without further issue and I was able to grant the user account access to the folder which had lost permissions when the original server had been replaced.