Adobe's system requirements for Flash 10.1 rather unhelpfully only list some distros and version numbers rather than actual library requirements. The oldest distro listed is Ubuntu 7.10 which was released in October 2007. As far as I can tell Vector Linux 5.8 came out December 2006. It's conceivable that there are library requirements that Vector Linux 5.8 doesn't meet.
Have you made sure that libflashplayer.so has global read and execute permission?
Are you using Firefox 2.0 or newer?
If you put about
lugins in to Firefox's location field, what do you see?
The output of
Code:
$ ldd libflashplayer.so
might be useful. It will list what shared libraries are required by libflashplayer.so. Whether it will list which ones are required and missing I don't know. If you are missing required libraries updating them will probably be a big task. You update one library and that requires another library to be updated and so on. You also risk breaking applications which depend on the libraries you're updating.