I went in and made the datastore directory 777 and then after I tried it the datastore_cache.php and all the files in the datastore directory changed to 644 and I can not changed them back to 777 now. I think it changed all the permisions. So I deleted the directory and reuploaded it again and made the directory and the file 777 again and tried it again and the file reverted back to 644 again. So now I am back to where I started.

The directory should be 777 and the file should be 666 (or 664)

Are you sure of this because VB only says that the file is suppose to be 777?
http://www.vbulletin.com/docs/html/datastore

I have this exact same issue occurring, did you ever resolve this?

No I never got this resolved. I just disabled it again. I got sick of people talking out their butts or not understanding the problem or not knowing what they were talking about. I ask VB.com and they said it was a server issue and would not explain. I talk to my server management team and they told me that it was a software issue with VB. I love VB but I hate it when ever you have something they don't want to help you with they always default to blaming it on the server.

I asked the VB team what was the problem and they said it was a server issue. I explained that I owned my server and asked them what would cause this on a server so I could fix it. They replied "Honestly I have no idea what would cause the server to change the file permissions like that". How can they blame it on a server if they don't know what would cause it? They were spouting off just to get me off there back because they did not have the answer.

I have upgraded my VB to the latest version but have not tried using the "datastore_cache" file since I upgraded. I just gave up. It pisses me off that VB would put this in the config file but not help you when you have problems with it.

Don't get me wrong, I love VB but when they don't want to help you resolve something they do not have an answer to then what can you do.

PS. If you ever figure this out please let post your results here to help me and possibly others.

If the files are reverting back to 644 after you change them to 777, this is most likely an Apache issue and is typically caused by the owner:group being set incorrectly.

This can also be caused by servers running cpanel and the automatic script running to fix insecure file permissions.

If the server is running php as a fastcgi, this could also cause a issue when the file owner:group is set incorrectly.

Make sure you main home directory, typically /home/username is actually owned:group'd to your username for your account.

but you said at the beginning of the post that all of this happened after you upgraded to php5 try reverting back to the version you had to see if it resolved.

not much of a server tech but , reading this it sounds like a php issue.

I could probably revert back and try it but that was almost four months ago. The other reason I really do not want to revert back to PHP4 is because VB is only going to be supporting PHP5 when VB 3.7 comes out.