Selective Forbidden error

I am experiencing a weird problem.

I have a contact form written in php, in several computers the page works without any problems, but in two specific computers, as i send the form i get a 403 error.

even weirder is, if the form isn't filled correctly, it doesn't give me the 403.

I gave every folder and file that might be related to that page 0755 permissions, so i 开发者_如何学JAVAdon't think that's the problem.

Anyone know what might be the problem?

Thanks!

Because you said that it works without any problems on some computers I want to say that it is probably a caching issue on those problematic computers. Try clearing your browsing history/cache and trying again.

If it still causes errors you would probably get better results if you post the HTTP headers that you receive from computers that CAN access the site and computers that CANNOT access the site so that we can compare the results. You can use Firefox's Live HTTP Headers to capture the output pretty easily.