First, see if the error message you are receiving is like the one shown below.
/usr/libexec/ld-elf.so.1: Shared object "libXaw.so.6" not found
Errors like these are caused by installing the net/cvsup port on a machine which does not have the XFree86 suite. If you want to use the GUI included with CVSup you will need to install XFree86 now. Alternatively if you just wish to use CVSup from a command line you should delete the package previously installed. Then install the net/cvsup-without-gui port. This is covered in more detail in the CVSup section of the Handbook.