Problem Solved!!
Thank you Vilian.
The problem is a "user error."
Image2pdf supplies 2 dll's - one uses "STDCALL" convention and one does not.
My new version of xHarbour ( 1.2 ) must have the STDCALL version and I was calling the "other" DLL file by mistake.
Following advice of Vilian, I call the "Image2PDF StdCall.dll" and everything seems to work fine now, as it did before.
There is no problem with FWH libraries, as long as the FWH libraries are listed before the xharbour libraries in the link script. I looked at the linker map and I believe that the FWH version of CALLDLL() is being used - not xHarbour CALLDLL()
So, Antonio, I apologize for wasting your valuable time, and the time of others who replied and monitored this topic.