Everywhere I go on google I get the same answer to this problem but it is the wrong answer for me. Originally I installed Subversion 1.5.6 for windows (i run Windows Server 2008
You claim that the cause of your problem is not the post-commit hook script but my hunch is that that is exactly the root of your problems. When your post-commit script runs, how does it get the files out of your Subversion server so that it can copy them to your web server? Does it not check them out? Besides, you say that everything was working fine until you installed the post-commit hook script.
I have worked in mixed-mode client/server SVN installation situations before, including TortoiseSVN as a client and I have never come across any incompatibilities as long as the clients that work on the same repository are the same version.
Could you please post the contents of your post-commit hook so we can elaborate further?