Is the timestamp on the .vtx file later than the source file's? Vortex should only need to open the source file if the .vtx is missing or older than the source file (or a module in use by it).
Yes, I can run one of the problem scripts at the command line. Interestingly, I also tried copying the .vtx file to a temp subdirectory, and it runs! But back in the main directory, it still doesn't run without the source file, giving the same error in my first message.
Are you sure the version of texis that is running from the web server is the same as your command line version? If different, recompilation is required.
My 2 cents... It's been known to happen that people have 2 versions of texis installed on the same machine and the one run from the command line was different than the one being run from he webserver CGI. It would be good to double check.