I always used the version from ports but the last night I decided to give the cvs version a try.
So I've downloaded the aMule-CVS-20070825.tar.bz2 snapshot.
The first time, with a minimal configuration, the build went fine.
Then I tried again with a more complex configuration but I faced the same problem and I think I've tried at least 20 times with different options: you can figure out the frustration!
Finally I had it successfully build again after doing cd src && touch Scanner.cpp Scanner.h.
I hope it will work for you too.