Update: The problem turned out to be unrelated to Inkscape, but I thought that the resolution may help others, so here it is: The folder containing the font was encrypted when I downloaded it. I removed the encryption [from the folder properties window], reinstalled the font, rebooted the computer, ...

I am using Inkscape .48 on a machine running Vista Business. I recently purchased and installed Trajan Pro-Regular, open-type. I restarted Inkscape, used the font, and it appeared that everything was working well. The next time I opened the file, the dropdown list said "font not found on system...