I've just added a bunch of taxi ways to EGDM and when I save it all appears normal. However if I close AFCAD and re-open the airport all the nodes are still present but all the links have disappeared. Is there something I've missed on this?

This sounds vaguely familiar. I think this happened to me once, but I re-did the changes and the problem did not come back. If the problem persists, you should Export the broken airport (to something like EGDM_bad.txt), then recover the original airport (using the new Catalog function in AFCAD.) Also Export that recovered airport (to EGDM_good.txt) and then you can use Notepad or any other simple text editor to look at both files and see what went wrong.My guess is some kind of file corruption. I know it's annoying, but if the problem does not persist then the best solution is just to repeat the changes starting with the original airport.

Thanks for the reply. I've tried the stuff you recommended and had a few more attempts around the place and have come up with the following:If the airfield I change already has at least one taxiway then all works fine and the changes I make save correctly and reopen ok.If the airfield I change (like EGDM or EGDC) do not have any taxiways then when I save close and reopen it only saves the nodes. the taxipath section of the text file if exported is empty. If I add a taxi path, press save and then export there is an entry in this section of the txt file. However if I then close and re-open the airport the taxi path has been lost.Is there something special about adding taxi paths for the first time?