Well, I'll confess; I've been compiling with CVEL.
In addition to re-compiling the code itself, the cvel.lib needs to be re-compiled under the Orbiter 2010 libraries. Once that's done, it works fine.
I re-compiled the cvel.lib based on the VESSEL2-based CVEL library, except that I updated it further to use the VESSEL3 construct. No other changes have been made. In principle, it would be possible to use the VESSEL3 communication facilities in the SDK to eliminate the need for cvelmessage.dll altogether, but that's probably beyond my skills and certainly beyond the limits of my available time.
I had meant to update the Sourceforge page with my cvel3 .lib, but it appears my Sourceforge account (which did have that access) has been purged long ago from disuse.
So, I'll need to push it to Orbithangar.