You are a little impatient, aren't you. My guess is, if anyone knew the answer, they would have told you. Since there's no answer yet I think no one has any.
But here's my two cents,
The factory I work in uses a lot of Exor UniOP touchpanels, which are programmed by your said Designer software.
Recently I went down to all of those panels to make backups of them, just to make sure we really have the working version in backup. Most of them went well, but some of them gave trouble, and a few with your same error message.
My guess is, it's a compatibility issue between a recent Designer 6 and an old panel.
On a few panels I tried to upgrade the Firmware of the panel but in one case it crippled the panel's brightness (can't see barely any).
I also tried older software like Designer 5 and got succes with that also.
Hopes this helps a bit, good luck.